Pitcher Results After 2nd Tommy John Surgery
With Jacob deGrom and Walker Buehler coming back from their second Tommy John surgery (TJS), I wanted to go back and look at how pitchers performed after going under the knife a second time. While I had high hopes this study would find some useful adjustments, the results were mixed and probably point to the pitcher being more of the same.
I started out with the list of guys who had two Tommy John surgeries in Jon Roegele’s database. Then using weighted innings, I found the difference between several stats over certain time frames.
Timeframes
- y1: Season before the 2nd surgery.
- y2: Season of the 2nd surgery.
- y3: Season returning from the 2nd surgery.
- y4: Season after returning from the 2nd surgery.
In all, 45 pitchers had a second operation, and here are their season-to-season changes with the average age at the operation being 29 years old. One other factor is that xFIP and fastball velocity (FBv) weren’t always available, so the count on them is a bit lower.
Note: I would have liked to subdivide this group up by years between operations, but the sample size is already too small.
| Seasons | Matched IP | K/9 | BB/9 | ERA | WHIP | ERA | xFIP | FBv (fastball velo) | Count | Count for xFIP and FBv) |
|---|---|---|---|---|---|---|---|---|---|---|
| y1 to y2 | 1155 | 0.4 | 0.2 | 0.39 | -0.01 | 0.39 | 0.11 | -0.15 | 27 | 25 |
| y2 to y3 | 1142 | 0.9 | 0.1 | 0.20 | 0.12 | 0.20 | -0.04 | -0.31 | 26 | 24 |
| y3 to y4 | 1139 | -0.1 | 0.7 | 0.88 | 0.17 | 0.88 | 0.25 | 0.44 | 28 | 26 |
What a mess, nothing makes sense… at all. ERA constantly increases while xFIP stays constant. Walks and strikeouts both trended upward. Fastball velocity up from season 3 to season 4 but strikeouts even. And yes, triple checked my numbers.
For me, the simple conclusion is that there is no observable trend. Here is one more test, from the year before the surgery to the season after.
| Seasons | Matched IP | K/9 | BB/9 | ERA | WHIP | ERA | xFIP | FBv (fastball velo) | Count | Count for xFIP and FBv) |
|---|---|---|---|---|---|---|---|---|---|---|
| y1 to y4 | 1268.314724 | 0.58 | 0.48 | 0.25 | 0.03 | 0.25 | 0.07 | 0.1 | 24 | 20 |
The pitchers got a little worse over the full time frame but some loss should be expected with the average age being near 30.
Overall, pitchers seem to return from their second Tommy John surgery and throw comparable to when they did before the operation.
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.
It is good information to know Jeff. My draft sheet comment about Nate Eovaldi having 2 TJ surgeries was not needed based upon this data. I love these statistical studies you do.
Yes very interesting. It means we should not lower expectations on pitchers coming off the 2nd TJ. I would have thought the opposite but the numbers don’t lie.