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Swing King: Tony Zych slides his way to the top

Tony Zych surprised us all in his brief stint with the Mariners in September.

Kirby Lee-USA TODAY Sports

In the course of conducting research and testing theories, there are occasionally times where, after pulling all the data, I find that the concept for an article just doesn’t work. It’s frustrating to be sure, but sometimes something within that useless data pokes its head out and inspires a new tack. This article is an example of that exact phenomenon.

Earlier this week, posted an article that gave us a deeper glimpse into some of the data Statcast had been recording in 2015. In the article, Mike Petriello gave us a glimpse at league average spin rates for each pitch type as recorded by Statcast. I had the brilliant idea of pulling spin rate data from Baseball Savant to compare to this newly revealed data. Unfortunately, Baseball Savant still pulls its spin rate data from PITCHf/x, which is mathematically extrapolated, not the TrackMan data which is physically observed and measured.

All that to say, the original idea for this post didn’t work out the way I wanted it to. But from the data I did pull, I noticed something that I found pretty interesting. Do you know which pitcher on the current roster threw the pitch that generated the most swinging strikes last year? Was it Felix’s changeup? Iwakuma’s splitter? Charlie Furbush's slider? None of the above. Anthony Aaron Zych’s slider generated a whiff almost half the time the batter swung.

Let’s take a look at an example courtesy of Jose:

Zych Slider

As Jeff Sullivan points out in this FanGraphs article, Zych’s slider has an unusual combination of velocity and movement. None of the components—velocity, horizontal movement, or vertical movement—stand out on their own, but together they make for a slider that is fairly unique in baseball. In fact, when those three components are considered, just one other slider comes close to mirroring Zych’s: Brandon Cunniff of the Atlanta Braves.

The pitch in the GIF above is pretty impressive on its own. It's a first-pitch, backdoor slider thrown over the inner half of the plate. Its clear C.J. Cron had no idea it was coming and gave up on the pitch almost as soon as it was thrown. He may have been taking the first pitch anyway, but the command Zych shows to get that pitch over the plate is definitely a plus.

Zych threw just 133 sliders in 18 1/3 innings last year. Among all sliders that were thrown over 100 times, his whiff rate of 44.62% ranked 43rd, putting him squarely in the top 15% of the sample. That might be impressive on its own but when you also consider the contact that was generated off the pitch, things get very exciting. When batters put the ball in play off his slider, they put it on the ground twice as often as they put it in the air. And when they did put it in the air, they popped up 80% of the time! Granted, we’re working with a sample of just 21 balls in play, but that’s some impressive contact management.

Tony Zych definitely has the weapon to defend his crown as the Mariners’ swing king. His slider has developed into a plus pitch and its helped launch him into the majors as an option out of the back of the bullpen.