Freddy Peralta’s Fastball(s)

In my last article, I did a Quick Look at Freddy Peralta and found his fastball fascinating. He manipulated the pitch to provide the look of different pitches by changing his grip. What I wanted to know is if he could get by with just a good, varying fastball.

First, everyone needs to take a trip over to Peralta’s game page at and examine the pitch groupings. Usually, different pitches form clusters when examining variations in break, velocity, and spin. Ignoring the possible changeup, he has two groups, fastball and curve. His fastball has an estimated spin which varies from 1300 rpm to 2500 rpm. Its velocity differs from 88 mph to 97 mph. The spin values on Brooks are interpreted based on the ball’s break. The spin rates may be off because Peralta releases really close to home as Jeff Sullivan documented.

Using StatCast values, the spin rates vary from 2330 rpm to 2740 rpm, or about 400 rpm. Still, depending on the velocity-spin mix, the pitch could perform differently, which is what I saw in his start.

One graph not shown on Brooksbaseball is the relationship between velocity to spin. This comparison sometimes helps to find different pitches but in this instance, the graph is also no help.

While Peralta has some variation, the values don’t group. So it’s one pitch. But it’s not.

So, I’m back to staring at graphs on Brooks and I just can’t be confident of a difference. By squinting enough, I possibly saw these two groups.

Rotating the ball 180 degrees gives the pitch two movements which have enough velocity-spin overlap that the pitch blurs into just one pitch.

I wanted to know if he could get by with just his fastball. If there was enough variance in the pitch, hitters wouldn’t be able to square it up. I spent a few frustrating hours trying to find an answer and came away with nothing. While his fastball showed some variation, caused by the two grips, other starters had more variation, a lot more. While he had an above average rate of variation, he wasn’t even in the top 1/3 of all 2018 four-seamers.

While I went down several avenues to find why his fastball dominated, I kept coming back to two areas of inquiry. One is testable and the other is a theory for now.

First, while doing some comparisons, I noticed Peralta’s fastball had a high amount of spin. Now, Mr. Spin Controversy (Trevor Bauer) created a metric which compares a pitch’s spin and velocity. By dividing a pitch’s spin by velocity, a person ends up with the pitch’s Bauer Unit. Normally,the Bauer unit is around 25 for four-seam fastballs. The value usually stays constant as the pitcher’s velocity changes.

In Peralta’s cases, he has a high Bauer unit, 26.9 which is good for 19th overall of 203 starters who threw at least 30 fastballs. The extra spin, when compared to a pitch at the same velocity, will make it harder for hitters to square it up.

No matter if the fastball is one or two, it’s a good pitch. Time will tell if he can get by with just it.

Second, I’d not be surprised if other starters use the two four-seam grips for a different movement. With Peralta, the whole baseball world noticed a rookie making his debut in Colorado while using just one pitch to throw a shutout. It’s possible that other pitchers who have one to three usable breaking balls haven’t had a deep analysis performed on their fastball. I’d not be surprised if some struggling pitchers give the second grip a try.

In all seriousness, he’s a unique pitcher for many reasons. It’s tough to find comparable pitchers when there are none. No no comparables, how are owners to know how he’ll perform. I feel it will take at least five more games to get a better understanding of him. For owners needing an arm, I think he’s an add but bench for now. He’s supposed to start this Saturday, so we can get a second game to add to the sample. He could come out throwing 50% curves. Who knows.

Jeff, one of the authors of the fantasy baseball guide,The Process, writes for RotoGraphs, The Hardball Times, Rotowire, Baseball America, and BaseballHQ. He has been nominated for two SABR Analytics Research Award for Contemporary Analysis and won it in 2013 in tandem with Bill Petti. He has won four FSWA Awards including on for his Mining the News series. He's won Tout Wars three times, LABR once, and got his first NFBC Main Event win in 2021. Follow him on Twitter @jeffwzimmerman.

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Thanks for the analysis Jeff. Seems like you and others are finding it difficult to find numbers to backup what we saw from his first start. I can’t help but want to jump to the conclusion that the two main contributors to his outrageous success in his start was:
(1) his deceptive delivery
(2) a lot of luck

Like trying to hit a pitching machine for the first time and noticing the ball drop from the hopper into the tunnel before the wheels accelerate the ball, hitters will learn to time up his delivery and there will be no deception anymore.