Mark Leiter Jr. had a disappointing start with the Yankees after being acquired from the Cubs at the trade deadline, with the team leaving him off the playoff roster until Ian Hamilton suffered an injury in the ALCS. Aaron Boone was quick to trust him, although it was more out of need than it was by choice, and the right-hander delivered some of the most clutch performances of their run to the World Series.
He’s shown up to Spring Training with added conviction it seems, as the right-hander has seen a pretty significant spike in velocity especially on his sinker. With some more power in his fastball and splitter, Mark Leiter Jr. has made some significant strides in the stuff department, and he could be poised for a bounce-back season in 2025.
Why the Yankees Could Get a Big Year Out of Mark Leiter Jr.
The Yankees brought in Mark Leiter Jr. to bring some swing-and-miss to a bullpen that seriously lacked it during the 2024 season, and he certainly brought strikeouts to the Bronx. With a 31.7% K% to just an 8.7% BB%, Leiter did exactly what you’d hope for in those departments, the problem is that he allowed more barrels and damage contact in the process.
His strikeout rate also declined by 3.2% after the deadline, and that 2.49 HR/9 made him impossible to trust in a big spot with runners on base. The key reason for his issues stemmed from a sinker that hitters could routinely punish, as he didn’t throw it nearly as hard as other pitchers especially out of the bullpen. For pitchers with firmly below-average fastballs, the margin of error location-wise is razor-thin, placing a ton of pressure to hit your spots knowing that hitters can still beat you because it can’t overpower anybody.
Over the offseason, this pitch seems to have been of importance to Mark Leiter Jr. who has upped his sinker velocity from 91.5 MPH last season to 92.7 MPH early on in Spring Training. Small sample size velocity gains happen all the time, but he’s almost immediately reached unprecedented territory in regard to velocity that would indicate these aren’t just random blips on the radar.
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In his most recent outing against the Twins, Mark Leiter Jr. ripped his three hardest sinkers ever recorded, and this goes all the way back to 2017 when he first broke into the big leagues. His splitter is also up a tick velocity-wise, but he’s thrown much harder sinkers before so I’m not sure if that is an outlier or something that comes with the improvements made mechanically to help him find some more heat on his sinker.
Hitters posted a .459 wOBA against Mark Leiter Jr.’s sinker last season, which is dangerously close to the wOBA that Aaron Judge posted during his historic 2024 campaign (.476). Throwing harder is going to make an immediate difference, and sandwiched in between a splitter and curveball that registered an xwOBA below .200 and Whiff% over 50%, he could have an arsenal that truly dominates.
People forget that Leiter Jr. possesses a truly elite K-BB%, the best predictor of future success among relief pitchers. Last season his K-BB% (25.0%) was the 11th highest mark among relievers with at least 50 IP, a mark that would have led the Yankees had he spent his entire 2024 campaign in the Bronx. His 33.6% K% was higher than David Robertson, Luke Weaver, and Michael Kopech, and yet all of them have much better fastballs than he did.
If Mark Leiter Jr. can throw a sinker that gets groundballs and easy outs for him in 2025, his two best weapons can shine and lead him to a strong season. We haven’t seen the sweeper or cutter up to this point and maybe that ends up being a conscious choice, with the Yankees trying to hone his best pitches instead of worrying about 6-7 offerings all at once.
The Yankees have cut down repertoires for relievers before, and a full offseason of work with the veteran right-hander could lead to his best season to date. The hype around him isn’t there because the first impression made was terrible, but that doesn’t mean the organization has lost an ounce of faith in him. If Mark Leiter Jr. can post an above-average GB% to go with that elite swing-and-miss potential, we could be looking at one of the Yankees’ best relievers in 2025.