Here's a look at some of the names who could be on the market and the roles in which they've been used (though admittedly not all fall neatly into one category)…

Closers

Glen Perkins (Twins)

The Twins are just one of two teams to regularly deploy a left-handed closer, and the other (Cincinnati's Aroldis Chapman) isn't even up for debate. GM Terry Ryan has turned away early inquiries on Perkins, which is understandable. Perkins is in the first year of a three-year, $10.3MM contract that contains a $4.5MM club option. He's pitched to a 1.82 ERA with 12.2 K/9 and 1.8 BB/9 in 2013, and he has a 2.38 ERA dating back to 2011. On top of that, the Minnesota native is beloved by his hometown fans. Interested parties would likely have to make a shockingly large offer to acquire the 30-year-old.

Setup Men

Oliver Perez (Mariners), Mike Dunn (Marlins), Scott Downs (Angels), Antonio Bastardo (Phillies), Mike Gonzalez (Brewers), James Russell (Cubs), Darren Oliver (Blue Jays)

Perez has risen from the ashes to rebuild his career as a successful late-inning reliever. After a disastrous three-year deal as a starter with the Mets, he returned to the Majors in Seattle's bullpen last season. In 65 2/3 innings from 2012-13, Perez has posted a 1.92 ERA with 10.1 K/9 and 3.4 BB/9. He's been terrific against both lefties and righties, and he earns just $1.5MM this season before hitting the open market.

The Marlins have flatly said that they don't want to trade Dunn, but some of that could be posturing, and teams will still surely be checking in. Like Perez, he's been effective against righties as well as lefties this season, holding each to an OPS under .670. His command is improved from 2012, though it's still shaky (4.4 BB/9), and he also whiffs about a batter per inning. Dunn is controlled through 2016, so an acquiring team would have to pay for three and a half years of his service.

Downs has obliterated opposing left-handers (.444 OPS) and held his own against right-handed hitters (.706 OPS). In the final season of a three-year, $15MM pact with the Angels, he is set to hit free agency at season's end. He's been one of the game's most effective lefty setup men since 2007 and has a bit of ninth-inning experience as well (25 saves in that time).

Bastardo's excellent strikeout rate has dipped a bit in 2013, but he's still whiffed more hitters than innings pitched with his typical rocky control. He's been effective against right- and left-handed hitters throughout his career, and he's earning just $1.4MM this season as a first-time arbitration player. The Phillies aren't clear sellers, but if they decide to move some pieces, Bastardo will be of interest.

Gonzalez is used primarily against left-handed hitters, though he hasn't been outstanding against righties or lefties. He's a free agent at season's end and earning just $2.25MM, however, which seems like a perfectly reasonable price for a 3.00 ERA, 10.9 K/9 and 4.6 BB/9. Both FIP and xFIP suggest that his ERA should be about a full run higher, however. The Brewers' pen has drawn quite a bit of interest thus far.

Russell's stock has fallen after he posted a 5.56 ERA in 11 1/3 innings in June. Forced to face more right-handed batters due to deficiencies in the Cubs' bullpen, he was hit hard and saw his sub-1.00 ERA soar. However, he's still at 2.78 on the season and has seven straight scoreless appearances (though he's totaled just 3 1/3 innings in that stretch). Russell is controlled through 2015, but his career splits suggest that he's more of a lefty specialist than a true setup man.

Oliver, strangely, has been hammered by lefties this season but dominated right-handed hitters. The seemingly ageless 42-year-old is a free agent at season's end but could be a big boost to a contender's relief corps if he can rediscover his typical form against lefties.

Multiple Inning Relievers

Tom Gorzelanny (Brewers), Brian Duensing (Twins), Charlie Furbush (Mariners), Brett Cecil (Blue Jays)

Gorzelanny has a long background as a starting pitcher, but he's been used primarily in relief for the Brewers. His final two appearances prior to the All-Star break were starts, however, and that flexibility is likely appealing to other clubs. He's more effective against left-handers but has gone multiple innings numerous times this season. He can be controlled via arbitration for the 2014 season.

Duensing has been jerked back and forth between the Twins' rotation and bullpen throughout his career, but his glaring platoon splits indicate that he's best suited for a role as a left-handed specialist. He's been unusually susceptible to left-handed opponents this season but has held them to a .583 OPS for his career (compared to .828 for right-handed hitters). The former third-round pick is under team control through 2015.

Furbush isn't a free agent until after the 2017 season, so there's no rush for the Mariners to trade him. He's been reasonably effective against righties and stifled lefties, and he's thrown more than one inning in 10 of his appearances so far this season. Teams in need of relief help would undoubtedly be happy to land a lefty of that ilk.

Cecil is holding righties in check for the first time this season and has worked an inning-plus multiple times as a result. Lefties have a sub-.400 OPS against him, and he's under control through 2016 as a Super Two player. The first-time All-Star would likely have a notable asking price.

Lefty Specialists

Javier Lopez (Giants), Joe Thatcher (Padres), Travis Blackley (Astros), Wesley Wright (Astros)

Wright has been hit by both lefties and righties this season but excelled against lefty swingers in 2012. He can be controlled through 2015 and is making just $1.03MM after going through arbitration for the first time this past offseason.

Lopez, Thatcher and Blackley have been used primarily for one or two outs recently, and all three have held left-handers to an OPS under .600, with Thatcher limiting them to a brilliant .458 mark. Lopez is a free agent following the season, while Thatcher is controlled through 2014 and Blackley can be controlled through 2016. Blackley has starting experience as 2012 with the A's, so he could theoretically be stretched out into a longer role, though his splits aren't encouraging.

For more on the 2013 trade market, take a look at Tim Dierkes' examination of the market for catchers, first basemen, shortstops, third basemen, starting pitchers and designated hitters as well as my own look at the market for second basemen, corner outfielders, center fielders and right-handed relievers.

Starters (click here for leaderboard)

Kendrys Morales (Mariners), Adam Dunn (White Sox), Paul Konerko (White Sox), Adam Lind (Blue Jays), Ryan Doumit (Twins), Carlos Pena (Astros), Raul Ibanez (Mariners)

There are some interesting names in this mix.  Ibanez has shown vintage power in his age 41 season, while Morales has been solid as well.  I think a lot of armchair GMs would recommend the Mariners trade both players to stockpile prospects and young players, though the team's real GM, Jack Zduriencik, has said he doesn't expect to aggressively market his players.  Morales and Ibanez will be eligible for free agency after the season, and some have wondered if the Ms intend to make a qualifying offer to Morales.

Dunn will have about $20MM left on his contract at the trade deadline, as he is signed through 2014.  Konerko, who has full no-trade rights, will have about $4.5MM left and will be eligible for free agency.  Both players could at least be useful in a platoon, though trading Konerko for a modest return or salary savings might be more trouble than it's worth given his status as a fan favorite.  The Sox would have to pick up some of the tab on Dunn.

It's happening entirely against right-handed pitching, but Lind is having a resurgent year.  The 30-year-old could provide a major offensive boost, but the Blue Jays have affordable club options for 2014, '15, and '16 on him and may not be inclined to trade him.  Pena and Doumit would be nice bench additions, but both are slugging under .400 this season.

Other Possibilities

Mike Morse (Mariners), Carlos Quentin (Padres), Chris Carter (Astros), Lucas Duda (Mets), Aramis Ramirez (Brewers), Alfonso Soriano (Cubs), Michael Young (Phillies), Justin Morneau (Twins), Melky Cabrera (Blue Jays), Jesus Montero (Mariners)

Here are nine potentially available players who have not been regular designated hitters, but might be good fits to spend a few months in that role due to defensive questions or in the name of preserving health.  Ramirez, a third baseman by trade, is eligible to return from the DL from a knee injury on July 22nd.  If the clock runs out for him in July, his salary makes him an August trade candidate.  Some of the more controllable players listed here, such as Quentin, Carter, and Duda, are unlikely to be traded but we won't rule it out.  Montero, currently at Triple-A, hasn't hit well and has the Biogenesis cloud over him.

Soriano, Young, and Morneau have full no-trade rights, so potential suitors would want to gauge interest in a regular DH role in advance.

Check out the other entries in our trade market series.

Current Closers

Jonathan Papelbon (Phillies), Kevin Gregg (Cubs), Francisco Rodriguez (Brewers), Steve Cishek (Marlins), Jose Veras (Astros), Tom Wilhelmsen (Mariners), Huston Street (Padres)

Papelbon is the biggest name of the bunch, but for the time being the Phillies don't sound like they're going to be sellers. Even if they go on a losing streak, general manager Ruben Amaro Jr. said he thinks Papelbon would be difficult to replace. Still, given Papelbon's contract and declines in strikeout rate and velocity, the Phillies would be wise to listen if a team in need decided to pay for the brand name closer by offering an elite prospect.

Gregg's once dominant numbers have taken a tumble recently, particularly in his final outing before the All-Star break in which he surrendered four runs in one inning against the Cardinals. Still, his 2.97 ERA (3.69 FIP, 3.56 xFIP) and 9.5 K/9 rate would be a welcome addition to any bullpen. As a free agent at year's end who signed a minor league deal this season, he's financially feasible for any club, and the asking price won't be all that high.

Rodriguez, like Gregg, signed midseason and has revived his status as a credible Major League reliever. He's sporting a pristine 1.19 ERA, though his 3.06 FIP suggests that number is due for some correction. With a 9.9 K/9 rate and solid command (3.2 BB/9), K-Rod figures to be attractive to any team looking for a closer or setup man. He's saved nine games for Milwaukee this season, crossing the 300 mark for his career in the process.

The Marlins don't want to trade Cishek, but there's something to be said for a rebuilding team cashing in on a reliever that's performing well. Still, with four years of team control remaining and a 3.24 ERA with 8.9 K/9 and 2.8 BB/9, the Marlins consider him a building block. Recent reports said a team would need to part with its No. 1 prospect to acquire Cishek, and if that's the case, he's likely staying put.

Veras figures to be as available as any reliever on the market. I examined him as a trade candidate last month, and he's improved his stock by firing 8 1/3 scoreless innings since (he did allow one unearned run in that time). Veras has 42 punchouts in 39 1/3 innings to go along with the best control of his career (3.2 BB/9). He signed for $1.85MM in 2013 (plus incentives) and has a $3.25MM club option for 2014, so he's plenty affordable.

Wilhelmsen briefly lost his job and has seen his strikeout rate dip in 2013 while his walk rate has risen — none of which can be good for his trade value. He's back in the closer's role now, but he's not yet arbitration-eligible and has four years of team control remaining beyond 2013, so the Mariners may not feel a rush to trade him.

Street's price tag is down thanks to a 4.15 ERA and a career-worst 5.4 K/9 rate. He's spent time on the DL again this season, so his $7MM salary in 2014 doesn't seem as reasonable as it was when the Padres extended him instead of trading him last July. 

Setup Men

Jesse Crain (White Sox), Matt Lindstrom (White Sox), Jared Burton (Twins), Chad Qualls (Marlins), John Axford (Brewers), Luke Gregerson (Padres)

Crain, currently on the disabled list, isn't a closer but might be the most coveted name on the relief market. In the final year of an affordable three-year deal, the 32-year-old has a 0.74 ERA following a historic scoreless streak. He could slide into the ninth inning for many teams or continue in the eighth inning role in which he has excelled. He should be healthy before the deadline, barring a setback, and numerous teams including the Rockies and Red Sox have been connected to him.

Lindstrom is also in the midst of a strong season. He has a $4MM team option for 2014 which seems reasonable, given his 2.87 ERA. His strikeout rate is down and his velocity has dipped a bit, but he's still averaging 94.9 mph on his heater. He also has an impressive 53.7 percent ground-ball rate.

Burton emerged as a brilliant setup man for Minnesota after signing a minor league deal prior to the 2012 campaign. His outstanding season last year netted him a cheap two-year, $5.45MM extension that will be appealing to other teams. He also has a team option for $3.6MM in 2015. Burton struggled in June but rattled off six scoreless innings entering the break, which may quiet some concern surrounding him.

Qualls has seen quite a bit of time in the eighth inning for Miami and posted a 2.89 ERA with 6.8 K/9, 2.2 BB/9 and a whopping 66.4 percent ground-ball rate. A free agent after the season, the Marlins have made Qualls available and it seems likely that his days in Miami are numbered.

Axford lost the closer's gig in Milwaukee almost immediately this season, but he's on a roll in a setup capacity of late. He hasn't allowed multiple runs in an inning since May 1, posting a 0.99 ERA with 27 strikeouts and 15 walks in 27 1/3 innings in that stretch. He's arbitration-eligible for a second time this offseason and as a Super Two player, will be arb-eligible twice more before free agency.

Gregerson is controlled through 2014 and in the midst of arguably the best season of his career. He's pitched to a 2.93 ERA with 8.1 K/9 and 1.8 BB/9 in 40 innings of work. He's earning just $3.2MM as a second-time arbitration player this season, though that number figures to rise considerably in 2014. Teams not willing to pay for a "proven closer" may look to Gregerson as a ninth-inning option, though he does have a notable platoon split.

Middle Innings Relievers

Ryan Webb (Marlins), Burke Badenhop (Brewers), LaTroy Hawkins (Mets), Scott Atchison (Mets), David Aardsma (Mets)

Webb is controlled through 2015, and Badenhop is controlled through 2014. Both are ground-ball pitchers with uninspiring strikeout rates, and Webb's command has taken a significant step backwards in 2013. The Marlins and Brewers don't need to rush to trade either, but both could be had by a team who is intrigued by their ground-ball rates and team control.

Hawkins and Aardsma are eligible for free agency following the minor league deals they signed earlier this season, while Atchison could be controlled through arbitration. Hawkins has the best peripherals of the bunch, while Aardsma has the best strikeout rate in a smaller sample. Atchison has only whiffed seven batters in his 18 1/3 innings, which doesn't do much for his value.

Change of Scenery Candidates

Joba Chamberlain (Yankees), Alfredo Aceves (Red Sox)

Chamberlain is a free agent at season's end, and his tumultuous fall from once-prized prospect has been well-documented. On the plus side, his velocity remains strong and he's struck out 25 batters in 23 1/3 innings this season. However, he's also walked 13 in that time and seen his ground-ball rate plummet to 34.7 percent. The Yankees have reportedly been pushing Chamberlain and Phil Hughes in trades, and there may be a contender willing to take a chance on his velocity and whiff rate.

Aceves was outrighted off the 40-man roster over the weekend, likely signaling the end of his time with the Red Sox. He's clashed with managers and coaches throughout his Boston tenure, most recently having his effort and intensity called into question in 2013. He possesses talent, as evidenced by a career 3.69 ERA (4.37 FIP), but Boston wouldn't get anything of note in a trade at this point.

For more on the 2013 trade market, take a look at Tim Dierkes' examination of the market for catchers, first basemen, shortstops, third basemen and starting pitchers, as well as my own look at the market for second basemen, corner outfielders and center fielders.

Rentals

Matt Garza (Cubs), Tim Lincecum (Giants), Josh Johnson (Blue Jays), Phil Hughes (Yankees), Jason Marquis (Padres), Edinson Volquez (Padres), Erik Bedard (Astros), Aaron Harang (Mariners), Mike Pelfrey (Twins), Joe Saunders (Mariners)

These available starting pitchers will be free agents after the season.  Garza appears a lock to be dealt, and seems likely to command a top 50 prospect or equivalent young player as the centerpiece.  With over $7MM remaining at the deadline, trading Lincecum would be complicated.  Johnson and Hughes would likely generate solid interest on the market.

Controllable Starters

Yovani Gallardo (Brewers), Kyle Lohse (Brewers), Bud Norris (Astros), Joe Blanton (Angels), Kevin Correia (Twins), Lucas Harrell (Astros), Barry Zito (Giants), Kevin Slowey (Marlins), Carlos Villanueva (Cubs), John Danks (White Sox), Vance Worley (Twins), James McDonald (Pirates), Alfredo Aceves (Red Sox), Ricky Romero (Blue Jays)

All of these players can be controlled beyond 2013 given their contracts or arbitration status, not that teams would necessarily be thrilled by the prospect.  Gallardo and Norris seem to be the names to watch here.

Currently On The DL

Jake Peavy (White Sox), Jason Vargas (Angels)

Peavy is projected to return from a displaced rib fracture Saturday against the Braves, so he could make three starts to prove his health prior to the deadline.  He's under contract for next year, and would jump to the top of the short list of potential difference-makers.  Vargas had surgery to remove a blood clot in his left armpit and is expected to return before the deadline.

Other Possibilities

Cliff Lee (Phillies), James Shields (Royals), Ervin Santana (Royals), Jeremy Guthrie (Royals), R.A. Dickey (Blue Jays), Jeff Samardzija (Cubs)

These pitchers are not currently believed to be available, but it wouldn't be a total shock to see one of them traded this month.  Lee is the best pitcher named in this post, though he has no-trade protection and is owed more than $70MM through 2015.  The Royals probably are not inclined to gut their rotation, though it would make sense to entertain offers for Santana if they are beyond the value of a supplemental round draft pick, as he is eligible for free agency after the season.  Dickey and Samardzija are controllable beyond this year, but it would be silly for their teams not to listen.

For the large-salaried players such as Lincecum, Danks, and Zito, keep in mind that trades can happen in August as well if they clear waivers or are claimed.

Check out our other posts in the trade market series here.

Here's a look at some of the names who could be on the move as we approach the July 31 non-waiver trade deadline…

Regular Center Fielders

Justin Ruggiano (Marlins), Alejandro De Aza (White Sox), Franklin Gutierrez (Mariners)

The Marlins don't want to trade Ruggiano, but he has an outstanding glove in center field to go along with a nice blend of power and speed. He strikes out a fair amount and doesn't have tremendous patience, but a .249 BABIP has deflated his overall batting line to .218/.288/.397 this season. He's under team control through 2016 and isn't yet arbitration-eligible, so the asking price will be high.

De Aza grades out as a poor defender in center according to advanced metrics, but he's spent the past two seasons as Chicago's primary center fielder and hit well in the process (.274/.339/.413). De Aza will be arbitration-eligible for the second time this offseason after making $2.08MM in 2013, and the White Sox are open to dealing anyone other than Chris Sale and Paul Konerko.

Gutierrez, predictably, has missed a signifcant portion of the season and is on the shelf without a clear timetable for his return. The impending free agent hasn't played in more than 100 games since 2010 and could be moved in August if he can get healthy.

Part-Time Center Fielders

Andre Ethier (Dodgers), David DeJesus (Cubs), Chris Denorfia (Padres), Rajai Davis (Blue Jays)

Injuries have pressed Ethier into center field duties this season, and the team may prefer to hang onto him given its recent surge in the standings. However, the emergence of Yasiel Puig along with the presence of Matt Kemp (if healthy) and Carl Crawford could allow the Dodgers to try to shed Ethier's contract. He's just one year into a five-year, $85MM contract but has hit a mere .274/.348/.409 over his past 162 games. That's hardly $17MM production, and there's been plenty of speculation regarding his situation already.

Denorfia and Davis don't play center regularly, but each has significant Major League experience at the position. Both are speedy right-handed hitters who hit left-handed pitching far better than right-handed pitching, so they could serve as a nice bench or platoon component to a contender. Davis is a free agent at season's end, while Denorfia is controlled through 2014.

There's no timetable for DeJesus' return from injury, but he's punished right-handed pitching this season in a return to center field action. He's already played more innings in center field this season than he has since 2008, however, so interested teams could look at him as more of a corner outfield option when healthy. DeJesus has a cheap club option for 2014, so he's more than just a rental.

Fourth Outfielders

Endy Chavez (Mariners), Dewayne Wise (White Sox), Ryan Sweeney (Cubs)

Wise and Sweeney are both on the disabled list, though Sweeney figures to return at or shortly after the trade deadline. As such, he could be moved in an August trade due to the fact that he's a pending free agent. Wise was recently sent on a rehab assignment and should be healthy before the deadline, but he hasn't hit much in 2013. Chavez has been worse at the plate and figures to be a DFA candidate for the Mariners as much as a trade candidate.

Other Possibilities

Alex Rios (White Sox), Colby Rasmus (Blue Jays)

Rios hasn't played center field regularly since 2011 due to De Aza's arrival in Chicago, but he has more than 3500 career innings at the position. He's hitting .278/.333/.432 with 11 homers and 19 steals, and a contending team in need of a center field upgrade as well as an offensive boost could see him as a fit. Rios is locked up through 2014 with a club option for 2015, so Sox GM Rick Hahn will ask for a significant haul.

There's no indication that the Blue Jays will be firm sellers, and even if they end up going that route, GM Alex Anthopoulos may prefer to hang onto his center fielder. However, at 11.5 games out of a first and eight games back from a Wild Card spot, a losing streak could push the Jays into that territory, and Rasmus only has one year of team control remaining before free agency. Interested parties would likely pay a healthy price to acquire Rasmus, who is hitting .251/.324/.475 with 16 homers and strong defense in center field (according to UZR and The Fielding Bible). 

For more on the 2013 trade market, take a look at Tim Dierkes' examination of the market for catchers, first basemen, shortstops and third basemen as well as my own look at the market for second basemen and corner outfielders.

Starters

Alex Rios (White Sox), Alejandro De Aza (White Sox), Norichika Aoki (Brewers), Giancarlo Stanton (Marlins), Andre Ethier (Dodgers), Nate Schierholtz (Cubs), Marlon Byrd (Mets), Alfonso Soriano (Cubs), Chris Carter (Astros), Raul Ibanez (Mariners)

Stanton and Rios are the prizes of this year's crop, though the Marlins have gone on record numerous times saying they won't trade Stanton. Rios is available and could command the largest return on the market, as he's controllable through the 2015 season. He slumped in June but is still hitting .277/.330/.442 with strong defense in right field. He hasn't played center regularly since 2011 but could move there in a pinch.

Ethier and Soriano represent players who could be acquired in salary dump deals, and both come with significant platoon splits. The emergence of Yasiel Puig has brought Ethier's long-term role with the Dodgers into question despite the fact that he's just one year into an $85MM extension. Soriano has been on the block for years, but the weight of his contract has made him untradeable. Now, with just one year left and solid power numbers, the Cubs may be able to move him to a team in need of right-handed pop. Soriano has been particularly lethal against lefties, batting .294/.328/.514.

Aoki should draw plenty of interest, following the news that his contract allows him to become a free agent following the 2014 season. His contract contains a small $1.5MM club option for next season. The three-time Japanese batting champion has hit .292/.359/.411 as a Major Leaguer thus far.

Ibanez is enjoying an unlikely career year in terms of power production, as he's already launched 22 homers. His OBP is a paltry .301, and he may not be a clear-cut starter in the outfield because because of his defense. However, he's handled both lefties (.904 OPS) and righties (.826 OPS) very well and would be particularly beneficial to an AL team with a need at DH.

De Aza is miscast as a center fielder, according to advanced defensive metrics, but he offers a nice blend of speed and power. Like his teammate Rios, he's controlled through 2015, albeit at a much more affordable price. De Aza is earning $2.08MM this year as a first-time arbitration player. He could factor into the team's long-term plans, but GM Rick Hahn will reportedly listen to offers on anyone aside from Chris Sale and Paul Konerko.

The 26-year-old Carter is controlled longer than any of these candidates, but it's a stretch to call him a left fielder and he's leading the AL in strikeouts. In just over 400 career innings in left, Carter's UZR/150 is -37.6, and The Fielding Bible pegs him at eight runs below average. He has legitimate 30-homer power, however, for teams that can look past his defense. Given the amount of team control he has remaining, GM Jeff Luhnow likely wouldn't want to part with him on the cheap.

Schierholtz is arbitration-eligible for a final time this winter and hitting a solid .275/.330/.510, though nearly all of that production has come against right-handed pitching. Just 31 of his plate appearances this season have come against same-handed pitching. He's available, but the Cubs certainly don't have to move him this summer. MLBTR's Charlie Wilmoth recently examined Schierholtz as a trade candidate.

Byrd is arguably the best minor league signing of the offseason, as he's hit .268/.313/.506 with a team-leading 15 homers for the Mets. He's hitting both righties and lefties well in addition to playing solid defense. Byrd isn't likely to command a significant return, but he can provide a boost to a contender with a need in the outfield.

Backups and Bench Bats

Jerry Hairston (Dodgers), Laynce Nix (Phillies), Delmon Young (Phillies), John Mayberry Jr. (Phillies), Endy Chavez (Mariners), Juan Pierre (Marlins), Jason Bay (Mariners)

There aren't many attractive options in this group, though Mayberry and Young have had respectable seasons with the bat. Young has played his typical brand of brutal defense, however. Hairston can play multiple positions and has hit .261/.311/.342 this season. Pierre isn't hitting much, but he's held his own against right-handed pitching and can still run. Bay and Chavez haven't hit well, though Bay has handled left-handed pitching well.

Injured Players

Josh Willingham (Twins), Mike Morse (Mariners), David DeJesus (Cubs), Ryan Sweeney (Cubs), Chris Coghlan (Marlins), Lucas Duda (Mets)

Willingham is out four to six weeks after undergoing arthroscopic knee surgery. If he can return in time for the deadline, he could be moved, but the Twins would be selling low on his power bat. He's hitting just .224/.356/.398 after trying to play through injury. Owed just $7MM in 2014, he's unlikely to clear waivers in August. It seems like the Twins would be better served to listen to offers in the offseason.

Morse was acquired this offseason in a three-way trade with the A's and Nationals but hasn't lived up to expectations. He's been on the DL twice already, and after homering six times in the season's first nine games, he's hit just .249/.316/.391. His injuries and slumping bat likely mean the Mariners wouldn't get much in a return, but as a free agent who won't receive a qualifying offer, Seattle has little to gain by holding him.

DeJesus was enjoying a fine year prior to a right shoulder sprain, but it's not clear when he will return. I examined him as a trade candidate in May, noting that he could net a respectable haul given his affordable club option. A broken rib will cost his teammate Sweeney the same four to six week period as Willingham, but he could still be moved in August for a nominal return given the fact that he's a pending free agent. He was hitting .295/.342/.527 in 121 plate appearances at the time of his injury.

There's no timetable on Coghlan's return as it stands, but the former Rookie of the Year is hitting .277/.326/.415 in a rebound campaign after falling off the grid from 2011-12.

Duda has been on the disabled list since late June but could provide a contender with some power if healthy prior to the trade deadline. His defense in the outfield is among the worst in the game, according to UZR, but he can also play first base and could DH for an American League team. He's controlled through 2017 and is not yet arbitration eligible.

For more on the 2013 trade market, take a look at Tim Dierkes' examination of the market for catchers, first basemen, shortstops and third basemen as well as my own look at the market for second basemen.

This year, contenders such as the Yankees, Dodgers, Indians, and Red Sox could be in the market for help at the hot corner.  Here's a look at the potentially available players.

Starters

Chase Headley (Padres), Aramis Ramirez (Brewers), Michael Young (Phillies), Alberto Callaspo (Angels)

It's been made pretty clear by this point that the Padres don't intend to trade Headley, and would like to talk about an extension during or after the season.  Still, it's hard to ignore the Padres dropping nine straight and Headley's solid play since the end of his abysmal June.  GM Josh Byrnes would surely at least listen to offers this month, wouldn't he?  

Ramirez, also one of last year's best offensive third basemen, does seem eminently available.  There are three problems with that.  One, he's 35 and may be slipping defensively, perhaps to the point where an AL team wouldn't expect or want him at the hot corner for all of next year.  Two, he's under contract for 2014.  That's not necessarily a problem until you see that he'll earn a $16MM salary plus a $4MM buyout on a mutual option, essentially making him a $20MM player next year (not counting a discount for deferred money).  Ramirez has shown repeatedly that he can provide $20MM worth of value.  However, bringing us to our third issue, he's slugging just .414 this year.  That may be nothing more than a month-long slump, but the timing isn't great for the Brewers if they want to get out from the contract, get back solid young players, or both.

Young, in his first crack at the National League, has fared mildly better than in 2012.  At this point the 36-year-old is a complementary offensive player with a poor defensive reputation and a good clubhouse reputation; a contender may pick him up mostly for that reason.  Callaspo is a similar player in some ways, but he's signed through next year.

Backups

Cody Ransom (Cubs), Luis Valbuena (Cubs), Kevin Frandsen (Phillies), Placido Polanco (Marlins), Jamey Carroll (Twins)

The Cubs' third base platoon has been highly effective, as their .766 OPS at the position ranks fifth in the NL.  Ransom can be under control next year as an arbitration eligible player, while Valbuena can be controlled through 2016.  Add in strong part-time work from Frandsen, who is under control through 2015, and the trade market features backup options who have outplayed many regulars in limited samples.

Other Possibilities

Lonnie Chisenhall, Will Middlebrooks, and Mike Moustakas were once among the best third base prospects in baseball, but development has stalled on all of them.  The Indians' Chisenhall, called back up on June 18th, has been playing well of late and seems the least likely to be included in a deal.  In general, I don't picture the Indians, Red Sox, or Royals giving up on these players this summer.

Biogenesis Effects

Alex Rodriguez is tied to Biogenesis, and could theoretically be slapped with a suspension shortly after making his season debut.  Regardless of Biogenesis, though, A-Rod's effectiveness and ability to stay on the field following January hip surgery is a huge question mark.  The Yankees would be well-served to explore reinforcements at third base with Kevin Youkilis on the 60-day DL.

You can also check out our trade market posts for catchers, first basemen, second basemen, and shortstops.

This year, contenders such as the Pirates, Yankees, Cardinals, and Reds could seek a shortstop in some capacity, while any number of non-contenders may seek to add to their prospect stash at the position.

Starters

Jimmy Rollins (Phillies), Alexei Ramirez (White Sox)

Much has been written about whether the Phillies, currently 7.5 games back, will be trade deadline sellers.  Even if they do go that route, the 34-year-old Rollins has full no-trade protection and is under contract through at least 2014.  The Phillies still have Freddy Galvis and did acquire backup John McDonald recently, so they have options if they find a trade partner and Rollins approves.  Ultimately I don't think the Phillies could get a lot back for Rollins, so it makes more sense to hang onto the city's longest-tenured athlete.

Ramirez is worth a mention mostly because the White Sox are out of contention.  The 31-year-old is an acceptable option at short, hitting .277/.305/.342 with great durability and a reasonable contract that runs through at least 2015.  The extended control could put some non-contenders in play for Ramirez, if he's even available.  I was surprised to see Ramirez's age; this is not a player in his prime.  I think the return would have to be interesting for the Sox to pull the trigger.  Ramirez is not a player they need to unload, and naming Gordon Beckham the full-time shortstop requires a leap of faith.

Backups

Omar Quintanilla (Mets), Adam Rosales (Athletics), Ronny Cedeno (Astros), Brendan Ryan (Mariners), Ruben Tejada (Mets), John McDonald (Phillies), Jamey Carroll (Twins)

It's always good to add veteran insurance; a glove man like Ryan could help a contender.

Other Possibilities

With 20-year-old shortstop prospect Javier Baez getting a promotion to the Cubs' Double-A affiliate recently, is there even a sliver of a chance the team would consider trading Starlin Castro?  Though Castro was not brought in by the Epstein/Hoyer administration, and he's not the type of hitter they generally prefer, a midseason trade seems highly unlikely.  Castro's terrible season would mean selling very low, high-walk shortstops barely exist anyway, and the front office made a major contractual commitment to him just last August.

With no regular spot for him, the Rangers have turned one of the game's best prospects, Jurickson Profar, into a temporary utility man.  If they are to trade him, they'd surely require one of the game's best players in return, such as the Marlins' Giancarlo Stanton.  There's no indication the Rangers are open to putting Profar in a deal, though.

Eduardo Nunez missed significant time with an oblique injury, but he's now the Yankees' starting shortstop until Derek Jeter's season debut.  The team seems unlikely to move Nunez given the uncertainty with Jeter's health.

Biogenesis Effects

A couple of All-Star shortstops have been linked to Biogenesis in the Padres' Everth Cabrera and the Tigers' Jhonny Peralta.  Having dropped nine in a row, the Padres' status as a contender is slipping, so they may not need to act if Cabrera is suspended.  The Tigers' alternatives include Ramon Santiago, Argenis Diaz, and Danny Worth, so I imagine they'd have to make an acquisition if Peralta is suspended prior to the August 31st waiver trade deadline.

You can also check out our trade market posts for catchers, first basemen, and second basemen.

More famously, Marco Scutaro was acquired by the Giants in exchange for Charlie Culberson. Scutaro's Herculean .362/.385/.473 batting line down the stretch helped propel the Giants to the playoffs where he won NLCS MVP honors by hitting .500 over the course of the seven-game series.

Here's a look at some keystone players who could be on the move in 2013…

Starters

Chase Utley (Phillies), Daniel Murphy (Mets), Rickie Weeks (Brewers), Gordon Beckham (White Sox), Darwin Barney (Cubs), Mark Ellis (Dodgers)

Utley, with his .279/.348/.510 batting line and plus defense, is the prize of the crop. However, there's no guarantee that the Phillies will part with a player who has long been one of the faces of the franchise. Any offer will need to exceed the value of a compensatory draft pick, as the Phillies will surely make a qualifying offer to Utley after the season given his play thus far.

Murphy is once again enjoying an under-the-radar season. The 28-year-old has been a league average hitter according to both OPS+ and wRC+ (each is an even 100) to go along with solid defense and good baserunning. He's hit .296/.336/.417 over the past three seasons and looks headed for double-digit totals in homers and steals in 2013. With two years of team control remaining, the price tag would be high.

Weeks got off to another brutally slow start, but he's hitting .316/.385/.571 with six homers since May 22. He's owed $11MM in 2014 with an $11.5MM option for 2015, and another three weeks of strong offensive play could grab a contender's attention. Milwaukee GM Doug Melvin could help his case by including some cash in a trade.

Beckham missed almost two months with a broken hamate bone this season, but he's hit well when on the field (.331/.360/.424). He's not hitting for power or walking though, so the primary source of his production has been a .384 BABIP that's exactly 100 points higher than his career mark. Because he's controlled through 2015, the Sox won't part with the former No. 8 overall pick cheaply, but they're reportedly listening to offers anyone other than Chris Sale and Paul Konerko. A career .250/.315/.384 hitter, Beckham hasn't lived up to expectations and could be a "change of scenery" trade candidate.

Barney doesn't hit much, but only Dustin Pedroia has graded out as a better defender at second (according to both UZR and The Fielding Bible) since the start of the 2011 season. He's not yet arbitration-eligible, so the Cubs would likely ask for a lot, but given their full rebuild, it'd make sense for them to listen.

Ellis is a free agent after the season, and even if the Dodgers position themselves as buyers, they could look to move him and pursue an upgrade. He's hitting .267/.310/.359. Others may not view him as a starter, but he's a reasonably competent bat with a strong defensive track record.

Backups

Nick Punto (Dodgers), Kevin Frandsen (Phillies), Cliff Pennington (D-Backs), Skip Schumaker (Dodgers), Jamey Carroll (Twins)

Punto, Pennington and Carroll all profile as glove-first acquisitions, though Punto has had a decent season with the bat (.260/.328/.320). Carroll hasn't hit much, but his batted-ball profile hasn't worsened from last season's solid offensive performance. A .259 BABIP has kept his overall production down, but even if that corrects itself, he'll never hit for power. Pennington has a $3.25MM guaranteed salary in 2014 and is arb-eligble for 2015, while Punto is a free agent after the season and Carroll has a $2MM vesting option for 2014 that triggers at 401 plate appearances.

Frandsen has been hitting well this year and has been particularly tough on left-handed pitching (.310/.429/.552). He's not a good defender, but he has MLB experience at all four infield positions and has even seen a little time in the outfield. He's arbitration-eligible for a second time this winter.

Schumaker hasn't done anything with the bat this season nor is he regarded as a good defender. The Dodgers would likely be happy just to shed his modest salary and open a roster spot. He could be a candidate to be designated for assignment if they do make an upgrade.

Other Possibilities

Danny Espinosa (Nationals), Ryan Roberts (Rays)

There haven't been strong indications that the Nats would part with the struggling Espinosa, but Anthony Rendon has hit well at second base since taking over after Espinosa's struggles and wrist injury. Teams could try to pluck Espinosa away from Washington, though the asking price would likely be steep, as he was viewed as a core player just a couple months ago. He did draw some trade speculation in late June.

Roberts was optioned to Triple-A Durham on Tuesday and doesn't seem to have a spot on the Rays' current roster. He hit .250/.303/.402 in 142 plate appearances this season and is regarded as a solid defender at both second base and third base.

For more on the 2013 trade market, check out Tim Dierkes' analysis of the trade market for catchers and the trade market for first basemen.

Starters

Mike Morse (Mariners), Kendrys Morales (Mariners), Justin Smoak (Mariners), Adam Dunn (White Sox),  Paul Konerko (White Sox), Justin Morneau (Twins), Carlos Pena (Astros), Chris Carter (Astros), Logan Morrison (Marlins), Ike Davis (Mets), Lucas Duda (Mets)

A closer look at the teams and situations listed here:

• Mariners: Morse and Morales are probably the most eminently available bats who are capable of playing first base, though neither has spent much time there in 2013 and Morse is currently on the DL with a quad strain.  Both players are free agents after the season and are unlikely to receive qualifying offers.  They've got some pop and don't come with ridiculous contracts.  Smoak, 26, was the primary piece acquired by Seattle upon sending Cliff Lee to Texas three years ago.  This year, he's missed time with an oblique strain and has continued to fail to show the power typical of a first baseman.  With arbitration eligibility ahead (not that he'll receive a large salary), the Mariners could choose to use Smoak in a deal.
• White Sox: I don't expect Dunn or Konerko to be traded, but they should at least be available.  Dunn's walks can't save a .200 batting average, his defense at first is not beloved, and he's owed around $20MM through 2014.  Konerko has started to hit somewhat in June, but he is a Chicago icon with no-trade protection.  He'd have to want to go to a contender, and with around $4.5MM left on his contract the money would have to be worked out with the acquiring team.
• Twins: Morneau has spent his entire career in Minnesota, winning the MVP in '06.  Like Konerko, he has no-trade protection, over $4.5MM remaining on his contract, and a slugging percentage below .400.  Trying to move guys like Konerko and Morneau might be more trouble than it's worth unless the players are completely on board and the teams can find significant savings.
• Astros: Pena is a veteran on a cheap one-year deal, but he's not hitting enough to bring back anything notable.  The Astros might rather just have him in their clubhouse.  Carter, 26, is tied for 12th in the AL with 15 home runs.  He also leads all of baseball with 108 strikeouts.  He appears to be the 30 home run, low batting average slugger we thought he was, which is OK but shouldn't prevent the Astros from listening.
• Marlins: Morrison's season debut was June 9th, as he was recovering from September knee surgery.  There's no particular reason to expect LoMo to be dealt, but he'll be arbitration eligible next year, and it's the Marlins.
• Mets: Considered a probable long-term piece for the Mets as the season began, Davis was brutal over 207 plate appearances to begin the season and was optioned to Triple-A.  A recall seems imminent, but as with the Mariners and Smoak, the Mets could just send him packing in a change of scenery deal.  Davis will probably be tendered a contract this winter, but not necessarily by the Mets.  Duda has drawn some walks and hit some home runs, but similar to Carter, there's no reason the Mets shouldn't listen on the 27-year-old.

Backups

The Marlins' Greg Dobbs should be available, and the Astros' Pena would fit in a backup role.

Other Possibilities

The Brewers' Corey Hart looks like an August trade candidate, if anything, as he's dealt with delays in his recovery from January knee surgery.  The Phillies' Ryan Howard would be nice to add in the larger part of a platoon, facing righties, but he's owed about $65MM through 2016 with good no-trade protection.  The logistics of a deal would be complicated, and the Phillies might not have the desire anyway.  The Nationals' Adam LaRoche gets a mention because of a scenario from ESPN's Jayson Stark, but it doesn't feel too likely to me.  The Giants' Brandon Belt has been OK, and as you've seen in this post, there are few available players who would serve as a clear upgrade.

Check out our Trade Market For Catchers post as well.

Starters

John Buck (Mets), Ryan Doumit (Twins)

Buck, 32, has hit .176/.263/.243 in 152 plate appearances since May 5th.  Anthony Recker serves as Buck's backup.  Mets fans await the big league debut of Travis D'Arnaud, the key piece in the R.A. Dickey trade over the offseason, as D'Arnaud recovers from a broken bone in his foot.  At last check, D'Arnaud was cleared to run in water.  If D'Arnaud needs more than a month, Buck could still be moved in August given his $6MM salary and lackluster hitting.  The Mets' goal should be modest with a Buck trade; he can back up somewhere and they can receive some salary relief.

Doumit, a switch-hitter, still has decent pop.  He's more of a catcher/designated hitter/occasional first baseman/corner outfielder.  The Twins gave him a two-year, $7MM extension in June of last year, so it's possible they'd prefer to retain him for 2014.

Backups

Dioner Navarro (Cubs), Hank Conger (Angels), Carlos Corporan (Astros), Jeff Mathis (Marlins), John Baker (Dodgers)

Navarro should be particularly available, since he's a free agent after the season.  He has a .468 SLG in very limited duty the last couple of years.  Conger and Corporan have also shown a bit with the bat this year as backups; their availability is uncertain.  Mathis made his season debut in mid-May after a broken collarbone, and has only 57 plate appearances on the season.  He's under contract for $1.5MM in 2014, with a club option for '15.

Other Possibilities

Should the Phillies adopt a more certain seller stance, impending free agent Carlos Ruiz should be available.  His season began in late April after he tested positive for Adderall, and then he later missed time with a hamstring injury.  We've yet to see whether he can be an asset offensively this year.  He's earning $5MM.  The Brewers' Jonathan Lucroy is signed through 2016, possibly '17, and I imagine they'll keep him.  Ditto for the Angels and Chris Iannetta, who is signed through '15.  I can picture the White Sox moving Tyler Flowers, though he wouldn't really help a contender.

Biogenesis Effects

The Yankees' Francisco Cervelli is currently recovering from a broken hand; the team has used Austin Romine to back up Chris Stewart in his absence.  If Cervelli is suspended for his connection to Biogenesis, the Yankees' desire to add a veteran could increase.  There's also Padres starter Yasmani Grandal, who has already served a 50-game suspension for testing positive for testosterone.  If MLB manages to slap a 100-game suspension on him, he could be done for the season.  The Padres would presumably turn back to Nick Hundley, but could at least look for a backup having cut Baker earlier this month.  They did subsequently add Chris Robinson to their Triple-A club, for which Rene Rivera is playing well.