Jake Arrieta Just Did Something He’s Never Done Before

We recently published a post about how Jake Arrieta increased his slider and curve usage against the D-backs Wednesday night. But there was another significant, noteworthy observation that came to light with the revelation of further pitch data. So important, in fact, that I think this is perhaps the result of a mechanical change or intervention with Chris Bosio.

Arrieta’s fearsome breaking ball has been described as baby slider or “slutter” because it doesn’t sweep across the plate like normal sliders do. Rather, the sharp-moving pitch is thrown upwards to 92 mph and with around 3.5 inches of horizontal movement. Brooks Baseball’s pitch classification algorithm categorizes Jake’s slutter as a slider, not cutter. That changed Wednesday night.

For the first time in Arrieta’s career, his 14 slutters against Arizona were categorized as cutters.

Why did Brooks Baseball suddenly change its classification of the pitch? Could it be velocity? Or horizontal movement? Vertical movement? No to all. Using those three measurements, there is no significant difference between Arrieta’s cutter from this most recent start and what has been called a slider throughout his career.

The difference was his release point.

This could be a very important trend, so much so that I need you to stop what you’re doing and really focus on the graph below. The data illustrates Arrieta’s horizontal release point since 2014 on a game-to-game basis. Bright red represents sliders, and the single dark red dot on the far right is the former Cy Young winner’s cutter against the D-backs. Notice how there is a YUUGE difference between his “cutter” release point and career “slider” release points. This graph shows that Arrieta was letting go of the pitch farther away from his body against Arizona.

The error bars, which represent the degree of variability among all pitches thrown in the single game, between Arrieta’s slider and cutter don’t even come close to one another. This suggests that this observation is so significant that the chance of this just being a fluke is roughly equivalent to the chance of the Phillies winning the World Series this year.

Again, Brooks Baseball has never before classified Arrieta’s slutter as a cutter, and the reason for this new classification likely has to do with the ginormous release point difference between Wednesday night and every start prior to it. Since his release point was so significantly different from his career norm, perhaps Arrieta made a conscious effort to change something.

The cutter classification of Arrieta’s slutter night makes it one of the rarest pitches in MLB since the league started tracking this kind of data. The bearded righty’s cutter release point hewed more toward third base than over 99.9 percent of cutters thrown since the genesis of the PitchFX era. Hitters simply have never seen something like this before. Ever.

This is a big deal.