If you felt like relievers were getting special attention this offseason, you weren’t imagining things. In a 2017-2018 winter that featured a free agent freeze the likes of which we haven’t experienced in recent memory, relief pitchers were the one position group that hardly seemed to suffer. They flew off the board remarkably early in comparison to the rest of the free agent crop this season; 17 of the 30 seven-figure major league free agent signings to occur on or before December 15th, 2017 (an admittedly arbitrary date) were relief pitchers.

I’ll follow that statistic up with the obvious disclaimer that one offseason doesn’t necessarily set a trend. But the buyer’s frenzy that took place in regards to relief pitchers this past offseason is in line with a startling trend in today’s baseball climate: reliable relievers are a more valuable commodity today than they’ve ever been before.

Notice the qualifier reliable. I’m not suggesting that the Warwick Saupolds and Alec Ashers of the world are suddenly any more valuable than they would have been five years ago. But the upper echelon of relievers, the ones who can be relied upon to come in the game and consistently get outs in the late innings over the course of a full season, the value of those relievers relative to other positions has increased from what it was in years past.

Of course, baseball is a game of context, and the word reliable doesn’t mean anything without tangible statistics assigned to it. Fortunately, the echelon of relief pitcher I’m talking about seems to have clearly defined itself across the past several seasons.

But before I get too much into those statistics, it’s important to set the context of this analysis by pointing out a clear trend in baseball: starters are pitching fewer innings than ever, leaving relievers to shoulder the remainder of the workload. Below is the number of total innings thrown by the starting pitchers in MLB games in the past three seasons…

2014: 28,992
2015: 28,223 1/3
2016: 27,412 2/3
2017: 26,787 1/3

With the starters getting quicker hooks, MLB relievers have seen their combined workload increase by 735 innings per season since 2014. Because of this, MLB bullpens were forced to handle an average of 73.49 more innings per team in 2017 than they had to in 2014. It looks like we’ll be seeing yet another decrease in total innings pitched by the starters this season; they’re on pace to throw about 26,542 total innings in 2018. With the way things tend to work in September, I’d be willing to bet that innings total will end up being even lower when the season comes to a close.

As one might expect, the number of qualified relievers last season reached its zenith in the modern era (155). But the number of relievers to throw at least 60 innings has remained within the same range across the past decade or so. There were 84 such pitchers in 2017, 85 in 2016, 79 in 2015, 82 in 2014, 93 in 2013 and 88 in 2012. So while we’re seeing bullpens shoulder larger workloads on the whole, we aren’t seeing an increase in the number of workhorse relievers who are able to remain healthy or hold down a job for the bulk of the season.

If an innings threshold doesn’t do it for you, perhaps an overall measure of effectiveness will. WPA, or Win Probability Added, is a measure of how much value a player has provided to a team based on performance in each plate appearance (or batter faced, in this case) in relation to the leverage of those situations. Though there’s been a significant uptick in the number of relief pitchers who accrued a WPA of at least 1 in each of the past several seasons, the number of relief pitchers who’ve managed a WPA of about 2 has remained largely the same. Here’s the breakdown by year (past five years) of pitchers who’ve met that 2.0 WPA mark…

2013: 25
2014: 23
2015: 24
2016: 23
2017: 23

It’s hardly a coincidence that almost every single one of the relievers to accrue 2.0+ WPA in a given season also threw at least 60 innings in that season. So while “reliable reliever” is a somewhat nebulous label, there are clear indications that we’re seeing an increase in the number of reliable relievers needed to make a complete ballclub, but not an increase in the number of reliable relievers in MLB on the whole.

While the above milestones are admittedly somewhat arbitrary, the fact that they’re holding so steady across a period of five years is probably not. The fact that there’s a need for more talented bullpen arms doesn’t necessarily mean that more of them will just suddenly appear. That would likely require a dramatic change in how teams draft and develop players, and it seems unlikely teams would place any additional emphasis on developing pitchers as relievers when the main strategy seems to revolve around turning them into successful starters, and shifting them to the bullpen if that doesn’t work out.

So to recap, bullpens in 2017 were forced to take on an average of 73.49 more innings than they were in 2014, but they aren’t developing any additional high-end arms to compensate for that. It makes sense, then, to think that almost all of those extra innings are likely going to replacement-level or near-replacement level relievers. That works out to nearly an extra out and a half per team game put in the hands of a relief pitcher who may be an up-and-down- or waiver-claim-type arm. Obviously it doesn’t work exactly like that, but the core logic checks out.

Perhaps that’s why a higher percentage of the free agent dollars have been going to relievers on the market lately. According to data pulled from Spotrac.com, total reliever earnings accounted for an average of 28.98% of free agent dollars spent across the past two offseasons. That’s a remarkable upgrade over the four offseasons prior; relievers averaged a 19.54% share of the total free agent spending, topping out at a 21.51% pie slice in 2013. Last year saw 15 different free-agent relievers earn eight-figure guarantees and 21 earn multi-year contracts, both stunningly high numbers in comparison with years past.

It’s not just the free agents, though. Teams have paid handsomely on the trade market for elite bullpen arms in recent years. The Indians gave up a hefty package for Andrew Miller at the 2016 trade deadline that included top prospects Clint Frazier and Justus Sheffield. The second Aroldis Chapman trade brought back a top 10 prospect in Gleyber Torres, and the Cubs parted with the highly-regarded Jorge Soler in order to get just one season of Wade Davis. Extensions for Brad Hand, Kenley Jansen and Felipe Vazquez in the past two offseasons guaranteed significant numbers of years and dollars, too. While no one of these transactions is necessarily an abnormality in and of itself, the general pattern of these reliever valuations and more beyond them are in line with the trend of top-flight bullpen arms being valued more in today’s game than in years past.

At its core, this seems a simple lesson in the laws of supply and demand. With a greater need for relievers that can be depended upon for consistency and high innings totals, contending teams are facing a sense of urgency in pursuing a crop of those relievers that’s remained the same size. Logically, said urgency would figure to drive up the market value of those players in comparison with other positions.

As is always the case in the game of baseball, things could change quickly. For instance, with superstar position players like Manny Machado, Bryce Harper and Josh Donaldson set to hit the market next year, it’s incredibly unlikely that reliever contracts will account for over a quarter of free agent spending, even with Craig Kimbrel, Andrew Miller and Cody Allen set to join the pool. Still, I’m willing to bet that the latter three end up with hefty paydays, with a handful of others surpassing expectations as well.