Jack Leiter’s MLB Success Will Depend On Fastball Location, Improved Secondaries


Image credit: (Photo by Bailey Orr/Texas Rangers via Getty Images)

The Rangers have announced that Jack Leiter will make his MLB debut on Thursday.

The news that the Rangers are bringing up Leiter is a useful reminder that with pitchers, development can take a very circuitous path from draft day to the major leagues.

At Vanderbilt, Leiter was often dominant. In a coronavirus-shortened freshman season and an impressive sophomore campaign, Leiter went 13-4, 2.08 for his college career.

He threw a 16-strikeout no-hitter against South Carolina one week and followed it up with seven no-hit innings the next week against Missouri. He allowed one run or fewer in 14 of his 21 college starts. That dominance helps explain why the Rangers picked him second overall in the 2021 draft.

Leiter’s pro career has had many more hiccups. Leiter came into this season with a 5.37 ERA. The Rangers twice sent Leiter to the development list to try and fix control issues that, at times, derailed his development.

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But to Leiter’s credit, he has made adjustments. When he came off the development list last August, he returned with a significantly reworked setup and delivery. He moved where he set up on the rubber. Leiter simplified his delivery, going from taking his arms over his head to a simple hand break. And most importantly, he slowed down his tempo, which had often gotten way too quick when he ran into trouble.

With a slower, more measured delivery, Leiter’s strike-throwing improved as he found it easier to stay on time with his arm. His strike percentage was under 60% before his delivery adjustments. Since the tweaks, he’s thrown strikes 64% of the time. Not coincidentally, his walk percentage is 5.2% this year. Before he was shut down, it was 13.8%.

When Leiter is on, he’ll strike out hitters in bunches, but his reliance on elevating fastballs does carry some risks as well, which have been apparent going back to his days at Vanderbilt.

Leiter’s flat plane and excellent carry allows him to get swings and misses when he locates to the top or just above the strike zone. But if he misses his spot, there isn’t much margin for error.

Leiter is extremely homer prone. He gave up 14 home runs as a sophomore at Vanderbilt, which is remarkable when you consider he gave up just 30 runs overall and only 48 hits. He’s given up 31 home runs in 192 innings as a pro.

Synergy Sports has pitch data for 29 of those 31 home runs. Only six have come against Leiter off-speed offerings, while 23 came off his fastball.

Here’s the location of swings and misses Leiter has generated with his fastball as a pro. When he’s at the top of the zone or just above it, he can dominate.

And here’s the location of fastballs that Leiter has given up home runs on as a pro.

Quality hitters can beat Leiter in the upper third of the zone at times. But when he gets middle or low in the zone, he becomes quite hittable. For his pro career, Synergy Sports data shows Leiter has held hitters to a .188/.340/.364 slash line on fastballs in the upper third of the strike zone or above with a 38% miss rate.

But Leiter’s fastballs anywhere else are quite hittable. Hitters have hit .336/.425/.640 with a 17% miss rate when Leiter is in the middle third or below in the strike zone.

Even the new-and-improved Leiter is exceptionally homer prone. He allowed five home runs in 19.2 innings last season after returning from the developmental list. He has allowed four in 14.1 innings this year.

Leiter throws his fastball more than most pitchers (60% of the time this year). He has shown this year it can work for him. But it will depend on how well he can locate. He has to avoid walks, as any traffic on the bases can turn survivable solo home runs (which he will allow) into two or three-run homers that can destroy a start.

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