The good and the bad about Stephen Gonsalves

Back on Monday, we were treated with the major league debut of Stephen Gonsalves. Well, “treated” as in we were promised Dairy Queen but then received a Dilly Bar, the replacement-level DQ treat. A top-3 prospect in the Twins system, the 24-year old lefty struggled mightily through 1 ¹⁄₃ innings as he lacked command of his pitches while getting knocked around by the Chicago White Sox.

On the surface, there’s no doubt that Gonsalves had a bad outing. He gave up six hits and four runs while walking two and hitting a batter. He also struck out three, but that could be filed in the “moral victory” column and that feat isn’t all that impressive when he faced 13 batters anyway (a slightly above average 23.1%).

While Monday’s outing was far worse than anyone could have predicted, parts of it could have been expected. Yes, of course the fact that he was nervous from it being his first major league start, but I’m thinking beyond that. For whatever reason, Gonsalves has had far worse control of his pitches this season. His walk rate in Triple-A this season ranked dead last among qualified starting pitchers at 13.4%. Compare that to his 9.0% walk rate during the other five years of his professional career and it’s clear that his control has especially been a problem this season. Thus, the walks and hit batter in Monday’s start shouldn’t have been much of a surprise.

However, Gonsalves has the tools to overcome his poor control. While he was extremely hittable against the White Sox, that was unusual for him. No one - not even the abundance of position players that have pitched this year - can run an .857 BABIP allowed like Gonsalves did on Monday, but it’s especially true for him. Not only has his batting average allowed over his minor league career been in the low .200s, but his minor league BABIP allowed has sat in the mid-.200s. While .300 is the magic number and any deviation above or below suggests bad or good luck, respectively, Gonsalves is one of the pitchers that has earned his good fortune thanks to his ability to induce pop-ups.

First, let’s take a look at the qualified major league leaders in infield flyball percentage.

We can see there’s a bunch of aces and oh hey there, it’s Jake Odorizzi! Now let’s take a look at the 2018 Triple-A pop-up leaders.

There’s Gonsalves entrenched at 11th overall this season among qualified Triple-A pitchers. What’s interesting is that his 23.0% infield fly rate is actually low for him. The only other times he’s created so few infield flies was during his first professional season in rookie ball back in 2013 (11.1% in 14 ¹⁄₃ innings) and last year during his first taste of Triple-A (24.1% in 22 ²⁄₃ innings). Otherwise, typically about 30% of Gonsalves’ batted balls have settled into an infielder’s glove throughout his career. That number will very likely come down as he gets more major league experience, but it seems that he should be fairly difficult to hit in spite of having middling stuff on the mound.

That stuff that was featured on Monday included a straight fastball that averaged about 91 MPH, a slider in the mid-80s, a low-80s change-up, and a big breaking curveball in the low-70s. Though nothing looked particularly interesting, the FX data from his abbreviated start caught my eye.

I’ll toss in some comparisons of some other pitchers in the majors.

The first FX plot belongs to Tampa Bay Rays phenom Blake Snell, who gets similar movement on his 4-seam fastball and slider, though with a lot more gas. Since Snell is better known, Rob Friedman a.k.a. “Pitching Ninja” has a great overlay gif of Snell pairing his fastball with his curve. Snell actually doesn’t induce that many pop-ups despite getting good “rise” from his fastball, however.

The second is from (admittedly bad) Barry Zito, but I care more that Zito was famed for his curveball and his movement and velocity is very similar to what we saw from Gonsalves. (Here’s Zito snapping off a curveball back during the peak of his career.) He also had good “rise” from his fastball as well and perhaps he serves as a better comparison to Gonsalves, though Zito’s fastball was much slower throughout his career.

Gonsalves had a bad start a couple days ago but there’s plenty of reasons to still have hope for him. With the Twins out of the running for a playoff spot, the team appears committed towards giving him at least another start and hopefully he has a better second start in the major leagues. He’s demonstrated that he can get outs in the minors and perhaps he’ll need to have a revelation similar to Jose Berrios, who struggled in his first taste of the bigs but had to learn that he didn’t have to nibble around the strike zone. That might be Gonsalves’ problem this season and I believe he could be successful even if he starts throwing more pitches in the strike zone. He’s shown the ability to get easy outs by inducing pop flies and repeating that skill in the major leagues will help him have a successful career.