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Looking for Blake Snell's second curve

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Are there two?

Adam Hunger-USA TODAY Sports

Yesterday I wrote about Blake Snell's debut, and analyzed his "stuff" using the PITCHf/x data. I found that he had a remarkable rising fastball, a very slow curve, and useful but not necessarily overwhelming sliders and changeups that slotted in at velocity points between the two.

I thought that was going to be it about Snell for a little while, but alert reader and DRaysBay writer Bradley Neveu noticed something in the Baseball America writeup of Snell' start that merits a closer look:

Snell, wearing No. 4, threw 12 first-pitch strikes, all catching the Yankees’ looking. He mixed his fastball, slider, changeup and two versions of his tenacious curveball well.

Two versions? Huh. Let's check.

Here's a chart looking at Snell's curveball movement with color denoting spin rate.


That's pretty clear. Spin the ball more and it'll move more. It's a smooth gradient from least-spinning to most-spinning, and it should be, because unlike Statcast, PITCHf/x doesn't observe spin directly. It observes movement and then uses physics to derive the spin (Jeff Long at Baseball Prospectus gave a good explanation of what that means for the two systems*).

*Someone in the press office at Statcast did a really nice job with the McHugh story and the furor about spin rates that it caused. Pet peeve of mine, so quick rant. Spin rate is a means, not an end, so in most circumstances, being able to see the spin rate directly (Statcast) isn't legitimately better than being able to see the movement (PITCHf/x). The McHugh story is really about Colorado, and about the Astros being clever enough to realize that the thin air was affecting his curve, and that if they plucked him down from the mountain, they'd have something different than what the Rockies had. The Astros guys (Mike Fast, for instance) ARE clever, and I'm pretty sure they could have done that with or without directly-observed spin rates.

Pitches don't leave a pitcher's hand the same every time, so a gradient, like what we're seeing, is what we should expect. If we're looking for two separate curves, though, what we want to find is clumps, and I don't see any. Maybe 16 pitches isn't enough for the clumps to identify themselves, but from what we have, I see no evidence of two versions in movement/spin rate.

Let's check the speed.


There's a little bit more to look at here, with a five mph range between the slowest curve and the fastest curve. Generally, the slowest curves Snell threw are all in the bottom left quadrant, so it may be that he threw one curve with more velocity and less spin (hence, less movement), and another with less velocity and more spin (more movement).

I circled two curves though, because they were Snell's best curves on the night, and because they broke out of that mold. The ideal curve is both hard, and has lots of movement.

As examples of plus versions of the curve, think about former-Ray Nathan Karns's curve, which moves slightly less but averages 80 mph, or of the those thrown by Clayton Kershaw and Collin McHugh, both of which average around 70 mph but have bigger movement in one direction than Snell's (down for Kershaw, to the glove side for McHugh).

A curve's effectiveness is a combination of both its velocity and its movement (spin). So it's possible that Snell has two versions, but what I'm more interested in seeing is one version that's more like the curves I circled in the picture.

Checking the Tape

The Baseball America article said something else about his curve, and had a quote from Snell:

His most effective pitch was the curve, which fooled the Yankees’ righthanded batters.

"I like to throw my loopy curveball," Snell said. "They were swinging at it so I kept throwing it. It was a good strikeout pitch for sure.

He threw it 16 times. It was swung at twice, once for a foul ball, and once for a popup. It was taken for a strike six times. Two of those times it was strike three, both to Brian McCann, who last time I checked was a lefthanded batter.

It was not his most effective pitch. It did not fool the Yankees' righthanded batters. They were not swinging at it.

I'm not criticizing Snell for misremembering exactly what happened in his first major league start or for not being able to articulate exactly what his process was. But Baseball America, please fact check.