Jack Leiter’s Rehab Start: A Breakdown

Last night, Jack Leiter pitched his scheduled rehab start versus the Las Vegas Aviators, the A’s Triple-A affiliate. I watched every pitch, so let’s do a deep dive about how it went:

I arrived at the Dell Diamond on Tuesday night to get an up close view of Jack Leiter as he undertook what is planned to be his only rehab start before rejoining the Rangers’ rotation either this weekend in San Francisco, or when the Rangers return to Arlington next Monday.

Jack arrived to the field approximately 25 minutes before first pitch, and quickly did some work with bands, plyo balls, and long toss with catcher for the evening, Tucker Barnhart. After about 5 minutes he made his way to the bullpen mound to get warm. The first few throws from the mound, Jack was wearing a band-aid over the blister on his right middle finger. However, he appeared to not particularly like how it was affecting his pitch shapes, so it quickly came off.

From there, Jack told Tucker he was going to focus on location and started getting into some sequencing. I took some videos to try and show as close as I can how great Jack’s stuff looks in person. The first sequence shown here is Fastball-Changeup-Changeup, and the second sequence shown is Slider-Curveball-Curveball. I really enjoy seeing things like this because it really helps put into play how these different pitches play off of each other. Especially with the first two pitches of the first sequence. Jack signals that he’s aiming a fastball at the top left of the zone. He misses a bit to the right, but it still sets up the next changeup. He starts the changeup in the exact same spot, but it just absolutely dives below the zone. Sometimes you’ll hear people ask “how could he swing at that?” Well…when both of those pitches look exactly the same coming out of the hand, the better question is: how are some hitters able to not swing at that?

I did want to show two more videos from his bullpen of a couple perfectly placed sliders at the bottom of the zone. I was able to capture one of them in slow motion, which I feel is incredibly fascinating to look at to analyze just how far Jack’s mechanics have come. Everything looks like it has purpose, is fluid, and is repeatable. It’s truly a testament to the work he’s put in, and it’s a pleasure to watch in person.

Ok, let’s move onto the outing. First things first, let’s get into some numbers:

Pitch Usage:

• FF: 30%
• SI: 22%
• SL: 18%
• CU: 17%
• CH: 13%

Strike%/Zone%

• FF: 63.1% // 52.6%
• SI: 83.3% // 75%
• SL: 72.7% // 54.5%
• CU: 60% // 40%
• CH: 50% // 37.5%

Movement Averages:

• FF: 15.4 iVB // 7.9 HB
• SI: 12.7 iVB // 12.4 HB
• SL: -0.2 iVB // -4.5 HB // 34 inches of drop
• CU: -9.6 iVB // -8.0 HB // 49 inches of drop
• CH: 0.0 iVB // 9.8 HB // 32 inches of drop

Stuff+/Pitch Grades:

• FF: 108 (67 Grade)
• SI: 94 (48 Grade)
• SL: 110 (63 Grade)
• CU: 102 (55 Grade)
• CH: 112 (74 Grade)

Individual Pitch Breakdowns:

Fastball:

I know, I know, stop me if you’ve heard this before: Jack Leiter has an elite fastball. I thought Jack’s fastball looked very good last night. As far as his stuff goes there have definitely been outings where it looked better, but that’s absolutely not to say that it looked bad in the slightest. A 108 Stuff+ grade is phenomenal, and I loved that he was consistently landing his spots. If your fastball is going to have a “down” day in the stuff department, then location immediately becomes paramount. Jack was able to consistently generate whiffs at the top of the zone on his fastball all night to the tune of a 40% whiff rate on it. He was able to get an oSwing% of 44%, and on those swings he generated an oContact% of 25%. A very good day for Jack’s fastball, and it’s not even at the best we’ve seen it.

Sinker:

Jack’s sinker last night is very interesting to analyze. With a Stuff+ grade of 94, the pitch graded out below average, yet Jack was able to be very effective with it. I don’t want to sound like a broken record, but his sinker never has to be more than what it is right now. It’s not a significantly lower grade than outings earlier this year, but he remains incredibly consistent at landing it for strikes. It always grades out as his highest zone% pitch, and it was the perfect addition to his arsenal this year to throw in fastball counts. It may have graded out the worst of all his pitches, but it also generated the lowest average exit velocity on all of his pitches at 61 mph. I personally love this pitch, and despite how disgusting the kick changeup was for Jack’s arsenal, his sinker is what I think will turn him into a top arm in this league.

Slider:

I thought Jack’s slider was absolutely disgusting last night. The theme for this entire article appears to be “consistency,” so I apologize if it’s starting to sound redundant at this point. I do feel however, that it is important to discuss, because so much of what maligned Jack last year was inconsistency. His pitch shapes were inconsistent, his delivery was inconsistent, and his performances were inconsistent. I’m left impressed time and time again just how much Jack was able to improve over one offseason. That’s not to discredit the work he put in last season either, as I believe that was invaluable to his growth. However just seeing him work in person you can just feel that this is a different pitcher than last year. I was displeased with a lot of sliders Jack threw last year. I thought too many of them looked like cutters, and I was unimpressed with his command of the pitch as well. This year I’ve done a complete 180 degree turn, and I couldn’t be more impressed. During his start last night Jack was masterful with his slider in keeping it low in the zone and having it tunnel perfectly off his fastball. He didn’t get a ton of whiffs on it with only a 28.6% whiff rate, but his command helped him generate a 40% chase rate on the pitch.

Curveball:

I will preface this by saying I’m not the biggest fan of Jack’s curveball. I understand and agree with it’s purpose in his arsenal, but I feel like often times he can fall a bit too in love with it, and it can have a propensity to get smashed if he leaves one up in the zone. Now that being said, I thought it looked very good last night. I need to do some more research, but I feel almost as if he’s changed the shape on his curveball. Last year it was definitely more of a 12-6 curveball that I thought was incredibly loopy and really didn’t care for the shape of, especially at the speed he threw it at. I’m starting to notice however, that it’s starting to take shape much similarly to that of Nathan Eovaldi’s. Which I think plays much better with the rest of his arsenal. He was very successful with it last night as it generated the highest whiff rate of any of his pitches at 66.7%. It grades out as only a slightly above average pitch, but stop me if you’ve heard this before: it doesn’t need to be anything more than that. Jack is always going to be a primary fastball, slider, changeup pitcher. His curveball doesn’t need to be anything more than a deceptive change of speed pitch that he’s able to throw in the dirt to try and generate chases, and I think he’s been doing a great job recently of throwing curveballs with purpose in the right situations.

Changeup:

I feel like I’ve run out of superlatives to describe this pitch. Praise be to Matt Festa for saving Jack’s career, because this changeup is absolutely filthy. It graded out last night as his best pitch with a 112 Stuff+ grade. What makes a changeup effective is how well it’s able to play off of your fastball. Essentially, you want as big of a difference as possible in iVB between your fastball and changeup. Typically you want at least a 10 inch difference, 12 if you really want it to be a whiff pitch. Jack was able to achieve a 0 inch iVB on his changeup to tunnel off of his 15.4 iVB fastball. That’s elite. And the fact that he’s able to average 92 mph on it? I simply do not care that the chase and whiff rates are not there on the pitch yet; that’ll come. What’s most important right now is being able to use it to the best of his ability. Don’t forget that this is still a new pitch. The fact that he’s been able to be this consistent and elite with the pitch shape is astounding to me. Control of the pitch will come with more time and experience with it. Despite having the worst zone% of any of his pitches, Jack is able to use his changeup effectively by using it to change speeds and set up his main primary pitches with low tunnels. This pitch will eventually be a game changer for Jack, but for now I am perfectly content with where it’s at.

Final Line:

• 4.2 Innings Pitched
• 1 Hit
• 1 Walk
• 4 Strikeouts
• 60 Pitches // 40 Strikes
• Top Velocity: 98.9 MPH

Overall Thoughts:

I was overall very impressed with jack’s performance last night. Typically the thing that handicaps most pitchers after a long layoff like the one he had, is command. Seeing in his bullpen before the game that Jack was putting a focus specifically on command even at the potential expense of his stuff was an incredibly mature thing to see. Time after time the thing I come away impressed by most in Jack is his mindset. He’s incredibly cerebral for such a young pitcher, and seems to truly know exactly what he needs to work on and what he should be proud of. Growth is never linear, and that’s something I tried to stress when talking to many of Jack’s critics last year. Not everyone is going to come into this league and light it on fire. You’re going to take your lumps, you’re going to struggle, but you’re going to learn a lot. And how you process that knowledge is what separates those who succeed and those who don’t. Jack is a sponge. He soaks up knowledge like I’ve never before seen in a young pitcher. You can see just watching him this year how much he’s taken in from Nathan Eovaldi and Jacob deGrom. Several times last night Jack employed a slide step towards the mound as a timing disruption to hitters, which Eovaldi does expertly well in each of his starts. I don’t think enough people realize how difficult it is to have consistent command when you’re employing timing disruptions. It’s so easy when you try to slide step to not finish through the pitch and have it finish high, but Jack did a stellar job on multiple occasions keeping sound mechanics while dispersing timing disruptions through his outing. You can see exactly what I’m talking about in the video I shared under his fastball breakdown. So much of hitting is based on trying to time up the pitcher, so anything you can do to throw that off is invaluable. Jack also did a great job limiting hard contact. Well, for most of the game. There was a terrifying (at least for me) moment where Jack was struck in the back with a line drive back up the middle. He ended up being okay and stayed in the game for another inning of work, but definitely a moment of pause.

It brought a smile to my face going to watch Jack last night and pick up exactly where he left off earlier this year. I truly believe that he will a very long and successful career not just because of his incredible talent, but due to his mindset. Jack has morphed from a “thrower” to a “pitcher,” right before our very eyes. I look forward to watching him rejoin the Rangers’ rotation, and I will continue doing these breakdowns for each of his starts, so stay tuned!