The New York Yankees’ bullpen has recently emerged as one of the best in baseball this season, dominating with both star power and back-end pitchers. This isn’t very surprising, being that they are famous for turning below-average pitchers into solid relievers. Just last season, they turned Luke Weaver, Jake Cousins, and Tim Hill from guys with a combined 5.57 ERA in 2023 to a 2.44 ERA as Yankees in ’24. Now, this year, we are seeing right-hander Mark Leiter Jr. undergo the same process, quickly turning into a high-strikeout, quality reliever.
The Transformation of Mark Leiter Jr.
Bad First Impression
The Yankees traded for Leiter Jr. on July 30, 202,4 from the Chicago Cubs, in return sending two prospects to Chicago. In 21 2/3 innings with New York afterward, the then-33-year-old put up a 4.98 ERA, allowing six homers but striking out 33. The potential was evident, but Leiter was allowing simply too much hard contact off his sinker (now his primary pitch). This year, though, he seems to have made some adjustments that have paved the way for a ton of strikeouts and limited barreled balls.
His wicked splitter has always been his put-away pitch, using it to rack up 77% of his strikeouts in ’24 and 66% this season. Now that pitching coach Matt Blake has helped him improve his fastball, his splitter has stayed just as effective in producing both strikeouts and soft contact.
More Ground Balls
Ground balls have been a pitcher’s best friend for as long as baseball has been around, and it’s no different today. The more a pitcher gets ground balls, the more likely they are to get outs. This is what’s been happening with Leiter Jr., with his higher ground ball rate correlating with his lower ERA. Throwing his sinker both more often and effectively, Leiter has seen his ground ball rate shoot up from 46.2% last season to 54.0% in 2025. Combined with a fastball that has seen an uptick in about 2.5 MPH (according to Baseball Savant), Leiter has become one of the Yankees’ best relievers this season. This is no small feat in a bullpen that features guys like Luke Weaver, Devin Williams, and Jonathan Loáisiga.
Leiter Jr has also cut down on the types of pitches that he throws, getting rid of a four-seamer and sweeper while adding a slider to the mix. This has, perhaps, helped him focus on commanding his main pitches, which is evident in his lower walk rate (8.6% to 6.7%). Taking into account a small bout of bad luck last season with an expected batting average against (BAA) of .224, it’s no wonder that Leiter has taken massive steps forward and become a force in the late innings for New York.
Another Elite Righty
With Mark Leiter Jr. emerging as an effective reliever, the Yankees’ bullpen is yet again performing better than expected. Ranking 6th in the majors in bullpen ERA and 5th in strikeouts, New York’s ‘pen is looking like it will continue to be an important asset throughout the season, and ideally into the postseason as well. Leiter Jr.’s performance this season is just another example of the Yanks’ prowess in creating effective potent arms out of previously low-quality pitchers.
