How does spin rate affect different kinds of pitches?

With the implementation of Statcast, the sabermetrics community is beginning to pay attention to several new metrics. One of the most intriguing is spin rate, which measures how many times the baseball rotates per minute while traveling to the plate. We have known for a while that a higher fastball spin rate correlates with swinging strikes and fly balls. It was also revealed that MLB teams like the Astros consider the spin rate of curveballs when targeting pitchers, as shown by their acquisition of Collin McHugh.

What we don't know is whether spin rate works the same way for each type of pitch. Actually, MLB teams probably do. Last season, they were given countless terabytes of Statcast data after every game, and they have probably conducted every kind of regression analysis imaginable to see what they can find. For accessibility reasons, it is harder for the rest of us to go that far in-depth.

Fortunately, baseball's Good Samaritan Daren Willman has integrated Statcast's spin rate data into his site, Baseball Savant. Last season, the kind of granular, pitch-by-pitch data that was offered from Pitch F/X was exclusive to MLB teams. But now, anyone can find the spin rate of any pitch, as recorded by Statcast's technology. Without further ado, here are the five most effective pitches from 2015, by Fangraphs' "Pitch Values" data, in addition to their average spin rates:

Out of 2015's five most effective fastballs, only Gerrit Cole's had a spin rate that was noticeably below-average. DeGrom and Kershaw were both around the league average, but they also get above-average extension towards the plate. Earlier, I wrote about how releasing the ball closer to home plate could have the same effect as a higher spin rate, which could be helping them. Since Cole also happens to throw 100 mph, it looks like a higher spin rate is ideal for four seam fastballs.

Things get a bit trickier for two-seamers/sinkers, especially since they are often used interchangeably. Brooks Baseball, another Pitch F/X site, actually doesn't make a distinction between these two pitches. Looking at the most effective two seam fastballs and/or sinkers, the key seems to be getting some kind of deviation from the league average, regardless of direction. However, extreme groundball pitchers like Dallas Keuchel seem to rely on low-spin sinkers.

It is tough to say how important the spin rate of changeups are, considering the fact that changeups rely primarily on slower speeds to mess with the timing of hitters. Still, offspeed pitches like the ones thrown by Edinson Volquez and Danny Salazar seem to suggest that less spin is better for changeups. While Toronto Blue Jays starter Marco Estrada successfully throws a high-spin changeup, it should be noted that he has an extraordinary amount of separation between his fastball velocity and changeup velocity.

When it comes to breaking balls, higher spin rates appear to be preferable, but the interesting thing is that the exceptions, like Chris Archer's slider and Clayton Kershaw's curve, are thrown from higher arm slots. Meanwhile, pitches like Tyson Ross' slider and Corey Kluber's curveball are thrown from ¾ arm slots. It is possible that pitchers with lower arm slots need more spin on their breaking balls, while pitchers with an overhand delivery can rely more on gravity to generate movement.

Another interesting finding is that spin rate doesn't seem to be an overall trait for pitchers. For example, Nationals ace Stephen Strasburg had a below-average spin rate of 2100 RPM on his four-seam fastball last season. However, his world-class changeup and curveball both had above-average spin rates of 1817 RPM and 2530 RPM respectively.

It is still unclear whether pitchers can improve the spin rate of their fastballs, but it does seem like they can manipulate the spin of every other pitch. Another example is Chicago Cubs ace Jake Arrieta. Last year, MLB.com's Mike Petriello pointed out that despite a pedestrian spin rate on his four-seam fastball, his four other offerings all had above average spin.

Taking it a step further, you have to wonder whether a pitcher is born with good "stuff," or whether it is an acquired trait. With pitchers like Arrieta, deGrom, and Kluber seeming to come out of the woodwork in their late 20's, it is possible that a handful of aces are waiting in the minors, not knowing that they are just a few small adjustments away from dominating in the big leagues.

Data is courtesy of Baseball Savant and Fangraphs.
League-average spin rates are provided by this MLB.com article.