MASH Report: Pitcher Spin Rates and Injuries

Today’s MASH Report is being brought to you by Ryan Butcher and Wade Davis. The pair were given a few days off recently to get themselves back together. Butcher was sent to the minor and Davis to the DL. While both may have needed a break, one interesting note exists about them missing time, both pitchers experienced a drop in their fastball spin rate right before the decision was made

These are the first two times I have seen a major league team admit that a pitcher’s spin was used to decide on how they handle a pitcher. It has been known for a while that changes in spin rate can help detect injuries. Eno Sarris talked to FanGraphs friend, Kyle Boddy about this issue.

From that discovery flowed others. “Spin-rate changes are actually one of the best predictors of injury,” pointed out Boddy, a fact that was confirmed as a known within many parts of the baseball community by multiple sources. At Driveline, pitchers have their spin rates monitored constantly for the earliest signs of unhealthy fatigue.

The problem for the general public, we have not had good access to pitch spin data until StatCast began releasing data last year. Here is a detailed look at the two pitchers whose spin rate change cause their team to act and can we make any conclusion from them.

Ryan Buchter

The first time I read about Butcher’s change in spin rate was in an article by Carlos Collazo where he stated:

The decision to send down Buchter comes after a week in which his spin rate was down, and a Friday night outing in which Padres manager Andy Green noticed some fatigue from the 29-year-old.

Buchter has averaged 92 miles per hour on his fastball this week, which is a slight tick below the 93-mph average that he managed through Aug. 13. In addition, Green said that his spin rate was down in August, which was another sign he could use a break.

So working through the information, his spin was down for a week before being sent down on Aug 20. I will use his BaseballSavant provided spin rate from the 13th to the 20th which includes three games. I will be using the spin rates for the week in question, the time before Aug 13, and since returning from the minors. He has for different pitches tracked by Pitchf/x (four season fastball, cutter, curve, and slider), but since he is a reliever, he sometimes goes games without throwing one or more of the breakers. For now, I will just look at his average fastball spin rate.

Time frame: fastball spin rate
Before Aug 20: 2295 rpm
Aug: 13 to Aug. 20: 2218 rpm
After Aug. 20: 2254 rpm

Looking at these numbers, his spin didn’t drop a ton during the three-game stretch. A half dozen times before the week in question, his spin rate averaged less than the 2218 value and nothing was done. Examining the games right before the demotion, a couple items stick out. First, his velocity had steadily dropped over 1 mph from 92.8 to 92.0 to 91.8 to 91.6 to 91.4 over 10 days. If this was the reason given for the break, I think many people would understand.

The other item I noticed was his spin rate on Aug 19 averaged just 2108 rpm. This was easily his lowest value of the season with the next lowest game at 2147 rpm (July 21). The drop of 200 rpm off his average, along with the velocity drop probably set off the delegated rest period. Coming back from the rest period, his spin rate is almost up to his yearly average and his fastball is averaging 92.5 mph.

Wade Davis

The information on Davis’s spin rate was stated by Todd Zolecki at

One front office reportedly balked at trying to acquire Royals closer Wade Davis before the Aug. 1 non-waiver Trade Deadline because it noticed a drop in the spin rate on his pitches. Davis landed on the disabled list with an elbow injury a short time later, although he is pitching again.

The Royals lost some trade value in Davis because of a lower spin rate. For Davis, I will look at the average fastbsall spin rate and velocity.

Wade Davis’s Fastball Spin and Velocity Readings
Time Frame Spin (fastball) Velo (fastball)
2015 2396 96.1
Season’s start to June 15 (probably healthy) 2396 95.2
June 16 to July 1 (two weeks before DL stint) 2348 96.1
July 15 to Aug 1 (sandwich DL stints) 2249 95.2
After Aug 1 to end of season 2268 95.1

Davis was showing about a 150 rpm drop off his fastball along with a 1 mph drop from 2015. Reading between the lines, I wonder if the front office saw his second games back from the DL as Davis slowly raised his spin rate from 2061 to 2153 to 2233 to 2253. If just looking at the 2061 game, I could see how a team would be worried about a -300 rpm change in spin.


In both cases, the mention of the spin rate linking to a likely injury is tough to verify or make any conclusions on. One item I have pondered after examining the two player’s data is how often a player sees their spin rate drop by 200 rpm or more. Here are the pitchers who over the last five days who have seen the largest drop in their average fastball spin rates (minimum 5 fastballs this past week).

Note: Some pitches do not get a recorded spin rate because of system error.

Pitchers Whose Spin Rate Has Declined in Past 5 Days
Name Total FB w/ spin values Average Spin (whole season) # of FB in last 5 days Average Spin last 5 days Difference
Ben Heller 42 2419 5 2204 -215
Marco Estrada 861 2404 7 2212 -191
Wade Davis 280 2360 5 2198 -162
Trevor Cahill 84 2225 5 2075 -151
Johnny Cueto 649 2327 19 2182 -145
Taijuan Walker 1035 2123 15 2008 -115
Cody Anderson 500 2458 18 2346 -112
Nick Wittgren 570 2076 11 1964 -112
Mat Latos 238 1984 9 1872 -112
Jim Henderson 448 2247 7 2136 -111

The first item to notice is seeing a 200 mph drop in fastball spin is pretty rare. Ben Heller is the only pitcher to meet this single criteria and he has only thrown 42 four seamers all season. The next pitcher sets off a bunch of sirens. Marco Estrada was cruising through the season and even getting some Cy Young consideration. Over the last four games, he has been hit around (.467 BABIP) and his ERA is at 7.29. Estrada has been surviving off the spin on his fastball which allows it to be as productive as a fastball 3 to 4 mph faster.

Estrada has seen a huge drop in his fastball spin rate this past game which will give his fastball less life and make it easier to square up.

I will be closely monitoring his next start.

And then Wade Davis shows up again. The same pitcher who hasn’t thrown in five days for some reason. I could possibly dive into each pitcher on the list, but they don’t have the huge drop like Davis and Buchter showed.

I am not sure when I am going to come back to the subject, but I do think I will begin acknowledging which pitchers have a larger than normal drop in other posts. Thoughts and suggestions on this subject are appreciated.

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.

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7 years ago

I guess the Strasburg news came out after this post?

Flexor Mass strain. NOT a UCL thing. They’re saying it was an acute injury, not an overuse thing. No surgery, just rest and rehab. Probably done for the year (inc. playoffs) but it’s not impossible he comes back.