It wasn't a simple road for Jack Leiter to get through his first MLB season. The son of 19-year MLB veteran Al Leiter, Jack was a dominant starter at Vanderbilt and was drafted second overall in the 2021 MLB Draft. It seemed like the younger Leiter was uniquely positioned to handle the mental and physical grind of professional baseball, but not many people expected that theory to be tested so quickly.
In his first professional season, Leiter posted a 5.54 ERA in 92.2 innings at Double-A. He missed plenty of bats, but he also gave up tons of hard contact. He came back in 2023 and spent the vast majority of the season at Double-A again, posting a 5.07 ERA but improving his strikeout rate from 25.6% to 31.3%. In 2024, the Rangers pushed him to Triple-A, and he responded with a 3.51 ERA and 33.3% strikeout rate in 77 innings before getting his first crack at big league innings. That debut did not go swimmingly, with Leiter posting an 8.83 ERA in 35.2 innings and seeing his strikeout rate drop to 17.9%.
Still, Leiter entered the 2025 season undeterred. He added a sinker to his arsenal and modified his changeup to try to help him against left-handed hitters. He garnered some buzz in spring training and then came out of the gates hot, pitching to a 3.48 ERA and 1.16 WHIP in his first 10 starts. The strikeouts still weren't near the level he had shown in the minors, but the progress was clear. After a tough six-start stretch in June and early June, Leiter rebounded over his final 13 starts, posting a 3.28 ERA, 1.19 WHIP, and nearly 27% strikeout rate.
It seemed that the 25-year-old had finally begun to figure it out, thanks to the evolution of his mental approach to the game.
"I think a lot of it's just how I've developed mentally, in my mindset and my mental preparation and my process," Leiter said after a spring training start this year. "I think the more process-oriented you get in this game, the better, especially this time of year, because you can drive yourself crazy with results... I think the more game reps you can get, which last year I was fortunate enough to have 29 starts in the big leagues, I think that just helps you evolve mentally in itself, but also with your routines, your preparation, your analysis of games."
So, how has Leiter's mental approach changed since his big league debut in 2024?
"It just becomes different, more refined. A game like today [allowing two runs on three hits in 1.1 innings], maybe three years ago, it would have just been kind of pure frustration off of results. But now it's about diving into each pitch and how I was executing. I like to break it down by each pitch type. Say my execution was down to, let's call it 60% from 68% last week, but maybe the cutter was kind of swaying that because it was only 3-for-9. Now it's like, okay, we have a direct point of emphasis for increasing my overall execution, because at the end of the day, execution is the name of the game, and the higher percentage that I can execute pitches, the more I'd be willing to bet on good results."
That shift in focus away from results has been crucial for Leiter, especially at this time of year.
"It's all about process. Understanding what time of year it is, and understanding what I'm trying to work on...Even the pitches where I wasn't so happy about the results, I think the shapes, the stuff, and the way that I was throwing it is definitely encouraging...At the end of the day, some pitches that get hit could have been a groundout to short. Obviously, they could always be better, but, again, you could drive yourself crazy, so I think the way to go is always a kind of positive mindset, continue to build off the positives, and learn from the negatives."
What does that look like for Leiter, specifically? Well, a big focus has been on attacking with the four-seam fastball. In his last spring training start, Leiter was encouraged that the pitch "was in the zone a lot." That's going to be important for him coming off a season in which his four-seam fastball had just a 52% zone rate, which was below league-average. That was a big reason why he added the sinker because he's able to command that pitch in the zone more often; however, being able to fill up the strike zone with both fastball variations could go a long way towards alleviating some of the command concerns that sprouted up after he posted a 10.4% walk rate.
The other focus for Leiter this spring has been on the introduction of a new cutter. The sinker last year was a good weapon for right-handed hitters to complement his four-seam fastball, but it performed poorly against lefties. His sinker allowed a 53% Ideal Contact Rate and a nearly 13% HR/FB rate to lefties, both of which were significantly worse than the league average. His four-seam fastball performed well to lefties, missing bats and not allowing much hard contact, but, again, it's not a pitch that Leiter has commanded in the strike zone regularly. The cutter to lefties could fill the same role that the sinker to righties did last year as an early-count strike pitch.
In his first spring outing, Leiter threw just two cutters, but both of them resulted in outs, so Leiter turned to it more often in his second spring start.
"It's a new pitch, and I'm working on it. I think what we saw with only throwing two [cutters] and getting two outs on them last week was to kind of see when we can and can't throw it in a game," Leiter explained after his start on February 28th. "Game results are the best feedback for that. Early on, I threw some really good ones, like in that [Kyle] Tucker at-bat in the first inning. I think at that point it might have just become like, 'Okay, that pitch is on today,” and then in the second inning, it wasn't quite the same. I think I was kind of just getting underneath it and just missing. Obviously, that's a pitch that we need to be in the zone at a high percentage, because it's meant to be thrown forward for contact. It's not a chase pitch.”
Understanding the bigger picture and what he's building towards is crucial for Leiter to take the next step in his development. However, there are some other things he'd like to see in addition to the cutter. He talked about the curveball feeling good out of his hand early in camp, and that would also be crucial for him. Even if Leiter uses the cutter to get ahead in counts against lefties, he didn't have a single pitch that had a better-than-league-average swinging strike rate (SwStr%) against lefties in 2025.
His slider, which he used 15% of the time to lefties, posted a 13.1% SwStr%, which was 43rd percentile, and was below-average as a two-strike pitch. His curveball, which he used 13% of the time to lefites had a 9.5% SwStr% but did perform well with two strikes, which suggests it could be a decent option when he mixes it in sparingly or, perhaps, is a pitch that he can find more comfort in this season and improve upon.
What we do know is that Leiter has the right mentality to figure that out.
