The Mets acquired Yennsy Díaz via the Steven Matz trade along with Sean Reid-Foley and Josh Winckowski in January. A rash of pitching injuries in the middle of the season brought both Reid-Foley and Díaz up to the majors, the former providing some spark and a few memeable moments, with the latter doing very little worth noting.
Díaz made 20 relief appearances for the Mets in 2021, most of them with the game well out of hand and only twice in a tie game, making him the backiest of the back-end relievers in the arm barn. He gave up 25 hits and 12 walks in his 25 innings pitched, and actually brought a meh 4.18 ERA into his final appearance before everything blew up. On September 13th against the Cardinals, Díaz gave up four runs in 1.1 innings, ballooning his ERA to 5.40 and earning him a one-way ticket to Syracuse for the rest of the season.
Díaz’s most notable appearances came in long relief: on four occasions he pitched at least two innings, all in mop-up duty, and never very effectively. He featured a fastball that routinely hit the mid-90s but also got smacked for a .355 WOBA. His only real secondary pitch was his changeup, which got hit at a similar rate but should’ve been hit much better, as batters tuned it up to an expected slugging percentage of .471. It certainly wasn’t ideal.
Díaz has featured primarily as a reliever in the Mets system after years of starting duties in the Blue Jays’ system, which may have contributed to his lack of seasoning in the majors. He didn’t fare well in triple-A Syracuse this season either, with a 6.75 ERA in 15 appearances, all in relief. One could attribute Díaz’s ineffectiveness to missing the 2020 season and adjusting to a new role, though an exceptionally low spin rate on his primary pitch might also play a key factor.
With two minor-league options left on his contract heading into next season, it’s likely the Mets will treat Díaz much the same as they did this season and bring him to the majors only in case of pitcher emergency. Even if that does happen, however, there’s little he showed this year to get Mets fans excited.