Using Curveball Spin to Predict Blisters
Pitching blisters were an afterthought just two years ago but the reported instances have jumped the past two seasons. Detailed accounts were written by Eno Sarris here at FanGraphs and Ben Lindbergh at the Ringer.
Throwing a curveball may be to blame according to Sarris:
But we can’t dismiss that chart completely. The players who have gone down with blister problems have thrown curves 14.9% of the time, far above the 10-11% baseball as a whole averaged over that timeframe. The players who ended up on the list more than once averaged 18.9% curveballs. Enough to say there’s some smoke here.
Here are curveballs rates for any pitcher mentioned at Pro Sports Transactions with a bister injury and their curveball usage.
| 2017 | CB% |
|---|---|
| Rich Hill | 38% |
| Brandon McCarthy | 22% |
| Edinson Volquez | 18% |
| Aaron Sanchez | 17% |
| Taijuan Walker | 13% |
| Carson Fulmer | 12% |
| League Average | 11% |
| Jharel Cotton | 8% |
| Johnny Cueto | 3% |
| Tyson Ross | 0% |
| 2016 | |
| Lance McCullers | 49% |
| Rich Hill | 42% |
| Seth Lugo | 17% |
| Brett Anderson | 15% |
| Clayton Richards | 13% |
| League Average | 10% |
| Andrew Cashner | 8% |
| Shane Greene | 2% |
Blisters are limited to just curveball pitchers but it is a larger percentage. These are only the reported instances of blisters but there are non-reported instances. These unknown blisters are even more important as it might point to a struggling pitcher such as Reynaldo Lopez.
I'm trying to figure out how Reynaldo Lopez's curve went from a plus grade (60) to 16% Swinging strikes in '16 to only 6% swinging strikes last year.
Cut its usage in half.
I wonder if he dealt with blisters (googled w/ no hits)
— Jeff Zimmerman (@jeffwzimmerman) November 29, 2017
Basically, Lopez quit throwing his best pitch from the previous season which had a 100+ rpm drop. He had the lower spin rate in his first major league start in August. He might have had the injury before reporting to the major league team. Without the minor league spin data, I decided to see if the spin changed on other reported instances and those can be related back to him.
The results weren’t as I expected them. Here is how the curveball changed for each instance.
| Name | Season | Changes in Curveball |
|---|---|---|
| Rich Hill | 2017 | Spin rates all over the place |
| Brandon McCarthy | 2017 | Saw spin rate jump from 2450 in ’16 to around 2650 |
| Edinson Volquez | 2017 | No rpm but usage did drop, 300 rpm drop before knee injury |
| Aaron Sanchez | 2017 | Spin was 100 rpm higher, 100 rpm lower (usage drop), & the same |
| Carson Fulmer | 2017 | Steady decline for 2650 to 2500 |
| Taijuan Walker | 2017 | Consistently +/- 100 rpm, did drop usage right afterward |
| Rich Hill | 2016 | Small 50 rpm drop before blister |
| Lance McCullers | 2016 | Usage trending down, spin up before injury, dropped spin in ’17 |
| Seth Lugo | 2016 | No trend at all, dropped spin in ’17 |
| Brett Anderson | 2016 | 100 rpm increase, back down in ’17. Usage drop in May ’17 before the back injury. |
| Clayton Richard | 2016 | Didn’t throw until after back from the blister. Then consistent, briefly threw in ’15 |
What a result hodgepodge. After staring at them a little too hard, I came up the following general points on blisters and curve.
- Rpm levels change, up or down, before the injury.
- Pitchers throw fewer curves once hurt.
- Pitchers change their spin the season after an injury.
Basically, if some aspect changes, put up a red flag.
In the case of Lopez, I would bet the injury either happened at the end of 2016 and he adjusted his usage and spin for 2017 or it happen during 2017 while in the minors. I’m intrigued by how he’ll use his curve next season. According to previous prospect reports, it was his best breaking ball. Will he bring it back or just use it as a show-me pitch.
So what can fantasy owners take from this? Nothing predictive. But if a pitcher, who throws a curve, is struggling, investigate the curveball usage and spin. They could point to a pitcher dealing with an unreported blister. Also, if a blister has already been reported, owners may consider the pitcher’s curve nonexistent. For some pitchers, they may still be productive. For others, they may need to be benched.
Jeff, one of the authors of the fantasy baseball guide,The Process, writes for RotoGraphs, The Hardball Times, Rotowire, Baseball America, and BaseballHQ. He has been nominated for two SABR Analytics Research Award for Contemporary Analysis and won it in 2013 in tandem with Bill Petti. He has won four FSWA Awards including on for his Mining the News series. He's won Tout Wars three times, LABR twice, and got his first NFBC Main Event win in 2021. Follow him on Twitter @jeffwzimmerman.
Jeff, is there anything that can be done by these pitchers to prevent the development of blisters? I think most repetitive tasks that cause blisters will form calluses over time and the blisters go away or lessen. Could these pitchers do some activity that would promote callus buildup other than pitching? I know this is a fantasy article, but got me thinging about prevention. I’m a red sox fan and watched years of Wakefield trying to protect his fingernails using random products and hardening techniques. Wonder if these curveball masters could do something similar.