Does a Velocity *Increase* Also Predict Injury? (A Primer)

Leading into the currently-young 2014 season, one of the biggest stories in baseball was the rash of pitcher injuries — with UCL injuries and Tommy John surgery seeming unusually frequent this year.

For Patrick Corbin’s case, in particular, my immediate thought was “Hm, I recall he increased his velocity last year”… which of course led me to wonder if the velocity increase actually caused his injury in some way.

I don’t know how common this line of thinking is.  So far as I can tell, the discussion of velocity and injury more frequently goes the other way, that a velocity decrease may be the first sign that something is wrong.  Or maybe this is actually a more common suspicion than I realize.  If nothing else, it seems to merit a closer look/increased discussion.

The logic here is simple: for most players, velocity only seems to decrease from year to year (although it may increase within a season).  So when a player bucks the usual pattern and increases velocity between years, you have to wonder what exactly he did.  At least some of the time, guys may be cheating a little (doing something not entirely sound, mechanically) to get that extra “oomph.”  This is of course is where the injury part enters.  If indeed some guys are cheating, maybe it’s only a matter of time before they blow out an elbow (or shoulder).

So can a velocity increase be a sign that a guy’s cheating and thus a future injury risk?  Answering this thoroughly takes some time and effort, more than I can probably spare this week, but I thought I’d at the very least get some reader thoughts.  Eventually I hope to look at guys from many different seasons,  comparing the injury rate of guys who did vs. did not see a notable velocity increase the preceding season.  (I’ll be using this list of TJ patients, which seems fairly complete.  Probably it would be better to add shoulder injuries, too, if someone has a list.)

For those curious, here are the 2012 and 2013 velocities for the five big names of this year’s “Tommy John cohort.”  Unfortunately there’s hardly anything that can be taken away from such a small list.  Harvey and Corbin had velocity increases (consistent with the conjecture), while the others did not.  But Beachy was coming off a previous Tommy John surgery performed in 2012, while Medlen’s 2012 was partially in the bullpen, so it’s not exactly clear what to make of their 2012 vs. 2013 velocities.

Name	2012 velo	2013 velo	Change
Matt Harvey	94.7	95.8	1.1
Patrick Corbin	90.9	92.1	1.2
Brandon Beachy	91.0	90.2	-0.8
Kris Medlen	90.0	89.4	-0.6
Jarrod Parker	92.4	91.5	-0.9

(Overall FB velocities in this table.  Maybe it would have been better to just compare 4-seam vs. 4-seam, but I didn’t want to have to worry about composition for now.)

It might be a few weeks before I myself have time for a closer look.  BUT, if anyone else wants to spearhead the effort sooner, please feel free to do so, and I’m of course happy to help.  As always, reader thoughts and feedback are welcome!