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Are the Houston Astros hacking pitcher spin rates?

Updated: May 2, 2018

Three weeks ago, Travis Sawchik of Fangraphs wrote that the Houston Astros “may have another ace.” The potential ace in question, of course, was Gerrit Cole. The same Gerrit Cole who suddenly increased his fourseamer spin rate from 2152 RPM to 2318 RPM, the fourth largest gain in baseball. He also increased his sinker spin rate from 2091 RPM to 2280 RMP, his slider spin rate from 2407 RPM to 2559 RPM, and his knuckle-curve spin rate from 2670 RPM to 2757 RPM.

While I was writing this, Eno Sarris of the Athletic confirmed that, yes, foreign substances can help players increase spin rate. I'm diving more into the specifics of Houston. I am not going to make any accusations, but rather present the data as I see it.

Generally, we understand spin rate as a skill. Not just a skill, but a “have” or “have-not” kind of skill. Driveline Baseball attempts to teach spin rate, but Trevor Bauer, the face of Driveline in the MLB, has only increased his spin rate by 83 RPM over four years. Cole basically doubled that gain in a single offseason. Three other Astros have increase their fastball by at least 83 RPM between 2017 and 2018.

Does that sound strange to you? Trevor Bauer certainly thinks so:

A couple weeks ago, I had a chance to ask John Mozeliak about spin rate, and whether the team understands if there are ways to change a player's spin skill organically. In a discussion which ultimately led to the announcement of a Pitching Lab in Jupiter, Mozeliak stated that, currently, the team generates its plan for a pitcher tailored to the skills that pitcher has. While there’s hope that the team may be able to manipulate pitcher spin rates in the future, it doesn’t appear that there is a clear answer right now.

I wondered, though, if there were any teams that had unlocked a key to the spin rate puzzle. We’d expect those teams to show improvements year-over-year and to consistently be among the “most-improved” teams, or the highest spin rate gainers. I decided to test that theory:

  • I looked at changes in spin rate for pitchers who three at least 30 IP in 2016 and 100 fourseamers in 2015; 30 IP in 2017 and 100 fourseamers in 2016; and 10 IP in 2018 and 100 fourseamers in 2017.

  • I only looked at players who were not moved between teams within the most recent season (2016 for set 1, 2017 for set 2, and 2018 for set 3). The spin rate change is credited to the team who the player pitched for most recently; i.e. the Astros in 2018 and Pirates in 2017 for Gerrit Cole.

  • My methodology is undoubtedly flawed, but hopefully good enough to serve as an indicator

Here are my results, by team:

The Astros are second! Milwaukee is first by a wide margin. Maybe I should have looked more at them. On another hand, Pittsburgh is showing the largest increase in 2018 at 69 RPM. Maybe they should’ve kept Gerrit Cole. I dunno, weird. But the Astros are second!

Additionally, the Astros are one of only five teams who have seen their pitcher spin rates increase each of the three seasons in question. The Astros increased their pitchers’ fourseamer spin rates by an average of 16.4 RPM in 2015. They increased them by an average of 20.4 in 2017. Then they did it again by 50.3 RPM (!!!) in 2018.

Next, I looked into specific players acquired by the Astros since 2016 and who proceeded to either play a full season in Houston in 2016 or 2017 or who are on the roster in 2018. That gave me this list:

  • Doug Fister

  • Justin Verlander

  • Mike Fiers

  • Charlie Morton

  • Hector Rondon

  • Gerrit Cole

  • Ken Giles

Here are their fourseamer spin rates in their last full year prior to joining Houston compared to their fourseamer spin rates in their first full year with Houston:

Four significant increases, and another small increase. Only one player, Hector Rondon, has experienced a decline and he has plenty of time to change that this year. Widening the net to match my criteria described above, Houston's pitchers have seen a year-over-year spin rate decline only 8 times out of 30 seasons. The MLB’s average increase in spin year-over-year is minimal, and players are just as likely to lose spin as they are to gain it. Houston is beating those odds by a wide margin.

Wading in a step deeper, I took the mean spin rates across pitch types for each of the above mentioned players, and graphed the average in their last full year before Houston and first full year with Houston. The pattern is even more obvious:

Every pitcher who threw a sinker gained RPM on their sinker after joining Houston. Same for sliders – the average increase on slider spin rate is 234 RPM. That’s nuts. Everyone but Morton gained RPM on their curveballs. Morton gained about 150 RPM on his cutter. The trend is clear: go to Houston, gain RPM!

Is Houston’s TrackMan giving hot spin readings? Probably not – last year, the team’s spin rates at home were only 13 RPM higher than on the road, and this year their home spin rates are actually lower than their road spin rates. Can’t blame the TrackMan.

Maybe the Astros have unlocked the secret to training spin rate. Maybe they’re doing it without foreign substances. However, if they are using foreign substances as Bauer appears to think, we should see an immediate, in-season increase for pitchers they acquire in-season. I checked for Justin Verlander. Guess what?

Well that's strange, isn’t it?

*Data courtesy of Baseball Savant.

**I focused the spin study on fastballs and breaking pitches, because it is widely thought that more spin on those pitches is better.


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