Mathematically Discovering Jack Leiter’s MLB Pitch Comps

In the months preceding the Major League Baseball draft, the buzz around the top draft-eligible pitchers start to come about. Baseball news outlets love to come up with Major League comps for these potential stars. And as fans we love to say “Oh this guy really reminds me of [fill-in the blank].” While this is fun, it is typically done just from an eye test. What if instead of just an eye test, we could find out which Major League arm actually compares to these draft prospects via the various pitch metrics we have available to us now? So I decided to find out for myself the answer to this question. The result of this question has allowed me to discover the closest Major League pitch comp for a given pitch in the arsenal of an amateur arm. (Example: [insert amateur name]’s fastball is closest to [MLB pitcher]’s fastball)

No better arm to test this on than this year’s 2nd overall draft pick and newest Texas Ranger, Jack Leiter.

My method for this project is using the Euclidean distance of the desired pitcher’s offering vs. all MLB offerings within the same pitch type. The metrics I included are average velocity, spin rate, horizontal break, vertical break, and spin axis. As a result, the lower the Euclidean distance, the closer the match is between the pitches. 

First, let’s take a look at Jack Leiter’s phenomenal curveball offering.

CURVEBALL

^{Top 5 Closest Major League Curveballs}

Pretty nasty and some good company in that list right? All-Star Freddy Peralta’s curveball comes in at number 1 on the list as the closest Major League curveball to Leiter’s offering.

SLIDER

Holy sword.

^{Top 5 Closest Major League Sliders}

Holy sword. 2x

While Leiter might be more well known for his curveball that falls off the face of the planet, his slider is also quite good with Zack Greinke’s slider measuring in at the second closest big league slider to Leiter’s slider.

FASTBALL

^{Top 10 Closest Major League Fastballs}

Leiter’s vertical break of -10.7 inches would place him in the top 10 of vertical break in Major League Baseball right now, meaning he would have some of the highest perceived rise in the league. We might have seen more impressive names at the very top of this list if Leiter was consistently more in the mid-90s like we have seen him in some starts. I believe we have reason to believe that is the case as Leiter has better vertical break than all of the guys on this list. I would have also loved to have added Leiter’s elite VAA as one of the comparison metrics but from my understanding, Savant does not currently provide that metric. Nonetheless, seeing the likes of starters such as Bieber and Gausman in the top 10 comps amongst other names is incredibly impressive. And Giovanny Gallegos’ very impressive fastball as seen in the GIF above comes in at number 4 in the pitch comp list.

This Leiter comparison to current Major League arms was super fun and I hope an insightful project. In this, we get to move past the MLB comps of just the eye test and move into what comps are closest based on various pitch metrics. While it’s fun to compare Leiter to current Major League pitchers, it will be an exciting ride to see how the newest top prospect of the Rangers organization paves his own road and career. One day soon enough we will be comparing the future college draft prospects to Leiter as he is making a name for himself in the big leagues.

All Major League Baseball is from Baseball Savant