MASH Report: Pitcher Injuries Continued

In last week’s MASH Report, I ran an up-to-date ranking of the of my pitcher injury finding metric, PAIN. The metric is supposed to find pitchers who are displaying traits of possible injuries. Reader, lostatlimbo, wondered:

“I’m also a little disappointed to see no mention of the % of actual injuries from high PAIN scores vs low to validate the data. Plenty of the pitchers with even negative scores have still been injured this season and naturally anything can happen at any time, but is there a significant statistical difference between the upper tiers and lower?“

Besides some initial testing on that season’s pitchers, I haven’t extensively run a recent test on the data. While information has always passed the eye test, it is time to dig a little more.

PAIN attempts to find pitchers who may be displaying signs of injuries from a loss of fastball velocity and/or pitch command (Zone%). I tinkered around a bit with the number after initially releasing the values, but the process has remained relatively constant. Today it is time to actually see how the results hold up.

One issue I have found with PAIN, is that pitchers with late-season high PAIN values, like Cole Hamels currently, make the metric look like it doesn’t work. So for my first test, I will look at pitchers who threw 120 innings in the previous season and find there next season PAIN value and if they went on the DL.

 

For pitchers, I looked from 2010 to 2014 to get the pitchers and then calculated these pitchers’ PAIN values and DL trips the next season (2011 to 2015). Over the five seasons, I looked at 599 pitching seasons and 250 of the pitchers went on the DL the next season. Here of the DL odds for different blocks of these pitchers.

DL Chances for Pitchers (min 120 IP in previous season)
Condition Overall Pain >= 90 Pain >= 50 Pain > 0 Pain < 0
On the DL 250 41 78 158 92
Total 599 72 158 356 243
Percentage 41.7% 56.9% 49.4% 44.4% 37.9%
The p-value for PAIN >= 90 compared to the rest is .0053 which is highly significant.

Truthfully, PAIN looks to be a nice predictor of injury even at the 50 level. The results are better than I would have predicted. A pitcher with a PAIN value over 90 sees this injury baseline injury chance jump from 42% to 57% or a 35% increase.

Now let me increase the amount of pitchers examined and go with same values for pitchers with just 30 innings pitched in the previous season.

DL Chances for Pitchers (min 30 IP in previous season)
Condition Overall Pain >= 90 Pain >= 50 Pain > 0 Pain < 0
On the DL 666 138 225 411 255
Total 1845 290 550 1057 788
Percentage 36.1% 47.6% 40.9% 38.9% 32.4%
The p-value for PAIN >= 90 compared to the rest is .000009 which is highly significant.

Again, the average pitcher’s DL chances jump significantly as their PAIN value increases. Right now I like how the data is holding up.

I know this week’s article wasn’t the most informative, but it will help with future PAIN references. For even additional information into this topic, I would like to improve the results by tweaking the numbers a bit. This research may not happen next week as I would like to use some Stat Cast batted ball data and see how it changes for hitters playing through known injuries.

Please let me know if you have any questions on this topic because it is easier to look at the information now with it fresh in my mind instead of at a later date.





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 three FSWA Awards including on for his MASH series. In his first two seasons in Tout Wars, he's won the H2H league and mixed auction league. Follow him on Twitter @jeffwzimmerman.

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