July 8: Arizona officially selected Diaz’s contract on Monday afternoon. The D-Backs optioned lefty reliever Joe Jacques to Triple-A in a corresponding active roster move. They already had a vacancy on the 40-man roster after releasing Tucker Barnhart, so that is now at capacity.
July 5: The Diamondbacks are “likely” to promote pitching prospect Yilber Diaz for his MLB debut next week, according to Steve Gilbert of MLB.com. The right-hander would get the ball to start Monday night’s series opener against the Braves. Diaz is not on the 40-man roster, but the Diamondbacks currently have an open spot on the 40-man, so they would not need to make a corresponding move to select his contract.
Diaz made his professional debut for the D-backs organization in 2021. After pitching to a 4.17 ERA and 3.66 FIP in 14 starts at Double-A between 2023 and ’24, he earned a promotion to Triple-A this June. In four starts with the Reno Aces, he has a 3.27 ERA with 28 strikeouts in 22 innings of work. On the season, he has an impressive 33.2% strikeout rate in 15 outings between Double and Triple-A. The 23-year-old is averaging just over five innings per start.
Diaz is currently ranked as the #16 prospect in the Diamondbacks system, according to MLB Pipeline. Baseball America and Keith Law of the Athletic both had him at #15 on their preseason lists. Eric Longenhagen and Travis Ice of FanGraphs were a little higher on Diaz, ranking him #6 and expressing more faith in both of his breaking balls (a slider and curve) to be potential plus pitches. Ultimately, however, all four sources agreed that the righty’s future is most likely in the bullpen. He throws a mid-90s fastball that can touch the high-90s; if his velocity were to tick up out of the ’pen, he could be a flame-throwing relief weapon.
Yet, for now, Diaz remains a starting pitcher, and he will take on the biggest test of his starting career on Monday. The Braves offense has struggled for much of the season, especially against right-handed pitching. Regardless, they’re going to be a far tougher opponent than a Triple-A club, and Diaz has hardly even faced much Triple-A opposition.
Although the rookie might benefit from a bit more seasoning in the minors, the Diamondbacks are a little desperate for starting pitching after Jordan Montgomery landed on the injured list last week. Rookie Cristian Mena made his MLB debut in Montgomery’s place on Wednesday, but the results were poor. He lasted only three innings, giving up four earned runs on four hits, three walks, and two home runs. Mena struck out just two of the 15 batters he faced, and he has already been optioned back to Triple-A. The only other healthy starting pitcher on Arizona’s 40-man roster who isn’t already in the rotation is Tommy Henry, who has a 7.04 ERA in 38 1/3 MLB innings this season.
