Tommy John Surgery Aging Curve

For the the recent The Hardball Times Annual, Brian Cartwright and I wrote a piece on Tommy John surgery. An aging curve on was cut from the article. I feel it provides significant insight so I will provide it now.

Pitchers generally get worse as they age with the one exception being that pitchers see an improvement in their walk rate until age 29. TJS pitchers show more year-to-year volatility, but over the long run the values stay the same, unlike the general pitcher population, which sees its values degrade. It is almost like the pitchers are getting a new throwing arm or at least a new ligament in the arm. Some survivor bias is present, as only pitchers that were able to return to pitch at a competitive level are shown. The bias exists with the overall aging curves, but not as much as those that have had Tommy John surgery.

3 thoughts on “Tommy John Surgery Aging Curve

  1. FYI, some thoughts about why we left the graph out: The two lines that stand out in the graph are the two big solid lines. Those appear to be the story of the graph. But they aren’t. The true story line is the variability with the TJS pitchers. The graph doesn’t make the point effectively. The TJS lines are dotted and lost in the spaghetti of other lines. Plus, the legend is very hard to read–which lines are dotted and which aren’t? This graph would have been particularly problematic in the e-book format, where graphs are too small. Plus, the survivor bias is a big deal. You can mention that in text, but it gets lost when people look at graphs.

    Of course, we could have worked on the graph format, but I think the article makes the point well.

    Just thought people would like the editorial perspective.

  2. it looks a lot like noise in the TJS data. I say this partially because of the lack of a clear trend (looks like you would have to 5-6 year periods together to get a clear trend) and because of the inexplicable lack of walk rate improvement by TJS pitchers after age 24… what’s up with that? looks fishy

Leave a Reply

Your email address will not be published. Required fields are marked *


6 − three =

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>