Tony Gonsolin: Learning the art of the offspeed pitch

Tony Gonsolin has learned to offset his four-seam fastball with a lethal offspeed repertoire, turning him into an effective big league starter.

With Will Smith, Dustin May, and Gavin Lux, it is easy to overlook the emergence of rookie pitcher Tony Gonsolin last season. The 25-year-old made his Major League debut in June, joining the rotation for a few turns in August, pitching effectively, earning a 4-2 record with a 2.92 ERA/3.86 FIP, along with an 8.32 K/9 compared to 3.38 BB/9 over 40 innings.

For pitching enthusiasts, what stood out the most about Gonsolin was his split-finger fastball. Baseball America ranked Gonsolin’s split, which they categorize as a changeup, the best among righty prospects in baseball. Gonsolin’s go-to pitch travels at 86.6 MPH, offsetting a four-seam fastball that reaches 93.6 MPH.

FanGraphs published an article on Tuesday with some great quotes from Gonsolin about how he developed his split/change. He mentions being drafted in 2016, “and my changeup was not good.” He went to an instructional league at the end of that year to start to develop the pitch, but really made progress in 2017 when he met Joel Peralta. At that point, he learned how to grip the ball in a way that turned the pitch into a “split/change” thing.

"He showed me a grip, and that kind of morphed into my own little split/change thing. I got a lot of reps with it in ’17 — I tried to throw it a bunch — and there were definitely days where it was better than others. Then, in 2018, the feel kind of just clicked for me."

Gonsolin used his split/change 25.1 percent of the time in 2019, most significantly as his put-away pitch, or the pitch he relies on to strike out batters when he has a two strike count. Hitters missed on 38.7 percent of the splitters they swung at from Gonsolin last year, according to Baseball Savant.

The key is his ability to make opposing hitters believe a fastball is coming by masking his throwing motion on offspeed pitches, as he explains in the FanGraphs article, “I’m basically throwing it like a fastball. Same intent, same arm speed. I’m trying to make it look like a fastball until it isn’t.”

Looking at Pitch F/X data on Brooks Baseball, we see that Gonsolin’s vertical release point on fastballs was on average 0.15 feet higher than where he released the split-finger. His horizontal release point had about a 0.23 feet difference between the two pitches. There was some variation for the keenest batting eye to decipher. Where he was most effective in masking his offspeed stuff was with his slider, especially in August, the month we have the most data points.

As you can see in the chart above, the vertical release point on his slider almost mirrored his four-seam fastball. And while opposing hitters batted only .182 against his split-finger, they were even more mystified by his slider, connecting for only one hit on 117 pitches thrown last season, according to Baseball Savant.

Tony Gonsolin might not be the most talked about young prospect on the Dodgers roster, but that speaks more to the organization’s depth of young talent than the lack of promise within the right-hander’s arm.