According to Baseball Savant’s pitch classifier, Keegan Thompson threw nine sliders in his most recent start against the Braves.

It was the first time, apparently, he has ever thrown a slider.

Pitch classifiers can be messy, and sometimes pitchers throw two versions of the same pitch type. Take Matt Swarmer for example, who has two types of sliders.

Also consider Kyle Hendricks’ two changeup versions, one that cuts and a second that tails away.

Nevertheless, it’s possible Thompson intentionally threw a new breaking pitch against the Braves, based on three observations: differential vertical break, velocity, and spin axis from cutters and curves.

First, as shown in the figure below, Thompson’s potentially new slider (SL) didn’t drop as much as his curve (CU), and there was essentially no overlap. Additionally, this breaking pitch had much more vertical break than his cutter (FC), and there was also essentially no overlap.

Second, the below figure shows that Thompson’s slider was thrown about 3 MPH faster than his curves, although there was a slight overlap in velocity.

Third, Thompson’s slider spin axis (degrees) was significantly different from all other pitch types. However, it was somewhat similar to his curve with a few pitches overlapping.

So what does this all mean? It means Thompson might have a new breaking pitch version that is almost like a faster curve without as much vertical break. Here’s what it looks like.

Still, while the data does suggest this is a new pitch type, we will certainly follow up with Keegan. If this pitch does hold up as a new slider, “Stuff” graders already rate it as a 55/80 in the small sample (above average).

All of a sudden, Thompson could have six unique pitch types, which could increase the probability he gets through a lineup more than two times.