Lingering Effects of Elbow & Shoulder for Pitchers

I don’t know for sure where I read or heard it, but an analyst mentioned they would never go near Luis Severino this season in drafts because of last season’s major shoulder injury. This claim is something I can investigate on the surface to see if anything sticks. Besides the numbers for shoulder injuries, I included the pitchers with elbow injuries.

For the analysis, I took the players who were on the IL for a shoulder or elbow injury in year one and then compared their next season projection and results. I had matching data going back to 2010 but didn’t use 2018 IL data because for some reason I didn’t clean up the last year’s data.

Then, I  took the average, median, and weighted average of each pitcher and grouped them by the days they were on the IL the previous season. These of these composite values each provide a unique insight. The average values can be quite a bit worse because one rogue 27.00 ERA can throw everything off. The median value is the one I prefer because it’s the 50 percentile results and it is how the random pitcher will perform. Finally, I included the weighted averages based on the innings pitched that season. The value is full of survivor bias since the pitchers who are getting good results will be allowed to keep throwing. Those that suck are in AAA.

I started cutting and dicing the groups to see if any interval stood out. I found a couple that work.

Starting with the shoulder injuries, I found the line at 100 days missed and here are the results.

Difference in Projection and Production From a Shoulder Injury the Previous Season
>= 100 IL Days < 100 IL Days
Average -5 0.14 0.73 -5.4 0.08 0.54
Median -2 0.02 0.39 -0.6 0.02 0.09
Weighted 15 -0.02 0.11 10.0 -0.02 0.00

While the WHIP didn’t move much, a 0.39 jump in ERA is nuts. Even the weighted value had a decent jump.

These values didn’t surprise Dr. Jesse Morse, “Shoulders are a complicated pain in the ass. Shoulders if you’re lucky, calm down with just a steroid injection and rehab, if that’s not enough then it’s not pretty.” Any long IL stay for a shoulder injury is not ideal.

And for reference, here are the pitchers who spent over 100 days on the IL for shoulder injuries last season.

Pitchers Who Were on the IL for 100 or More Days With a Shoulder Injury
Name Days
A.J. Minter 189
Arodys Vizcaino 172
Austen Williams 164
Brett Kennedy 187
Clay Buchholz 107
Danny Salazar 128
Dellin Betances 174
Felix Hernandez 104
Jeremy Hellickson 103
Luis Severino 176
Sean Manaea 160
Tony Cingrani 189

When I moved over to the elbow injuries, the results didn’t make sense.

Difference in Projections and Production Do to an Elbow Injury the Previous Season
>= 60 IL Days < 60 IL Days
Average -4 0.09 0.68 -18.3 0.15 0.90
Median -1 0.01 0.15 -11.0 0.07 0.11
Weighted 15 -0.01 0.04 -1.4 0.02 0.19

That’s right, the shorter IL stay meant worse results. The jump is with WHIP and a small ERA increase for the short IL stays. All but the median ERA value are worse for the short versus long IL stay.

None of the medical people who I talked with could explain why this happened. If it was in-season, the results might make sense with the pitcher possibly coming back from the IL too soon. Maybe elbows need at least two months to fully heal, but if the pitcher comes back early they develop bad habits? I’m sure some narrative could make sense but it’s hard to find one.

I’m going to go with an approach I’ve always had, try to minimize my exposure to pitchers with elbow and shoulder injuries. Additionally, I’m going to completely say away from those with extended stays on the IL from shoulder injuries.

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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The shoulder is a hard pass for me, I agree. Even elbows…if I’m not getting a big discount, I’m not interested and then only selectively. A good example of that this year is David Price. I’ll pick him up, but only later. Too many other good pitchers coming along to worry about those with injuries. Sadly, one of my favorite Rays Brett Honeywell falls into this category. I hope he makes it back, I hope he’s a star, but logic tells me he will never be productive or if he is it will be as a reliever of some sorts.