MVN - Most Valuable Network

The mystery of Troy Percival

While doing a wee bit of research for another piece that I was writing, I came across a small mystery in Troy Percival’s stat lines.  Open that up for a moment and take a look at his BABIP column over all the years that he’s been pitching.  (Prefer a graph?)  The numbers struck me as a little strange.  They’re almost all below .300.  (The one and only exception is 1997, when he had a BABIP of .313.)

BABIP is generally considered to be a matter of random fluctuation around a league mean, and the league mean is usually .300.  There’s a small mountain of evidence that says that there is very little repeatable skill in a pitcher’s performance on this particular stat from year to year, no matter how you slice it.  It looks like there’s a tiny bit, but randomness is far and away the bigger piece of what’s going on.

Then there’s Troy Percival.  From 1995 to 2004, he generally threw a little more than 50 innings a year and faced between 200-250 batters.  Again, only once was his BABIP above .300.  In 2005, he started giving up homeruns like crazy for the Tigers and soon was out of baseball… for a year.  His BABIP in 2005, however, was .192.  Then, last year, he caught on with the Cardinals and posted a .215 BABIP in 40 IP.  This year, he signed a contract with the Rays and has put up a mere .152  Assuming that BABIP fluctuates completely randomly and that I’m as likely to be above the mean as I am below the mean (a 50/50 shot), the chances of Percival being below the mean in 12 out of 13 seasons is about 0.17%, round it to 1 in 600.  Not astronomical odds, but certainly not odds I’d want to stake my life to.

Now, given that the BABIP reliability numbers that we have aren’t zero (just very very low), perhaps there can be a case made that Percival has a particular skill that we haven’t yet appreciated and that he’s not that lucky.  Still, there’s something a little mysterious about his statlines.

This entry was posted on Saturday, May 31st, 2008 at 10:23 am and is filed under Uncategorized. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.