Monday, January 18, 2010
Introducing TRX
Posted by Pat AndriolaAs a lover of sabermetric pitching analysis, two of my favorite stats are unsurprisingly xFIP and tRA. xFIP wisely takes into account the factors that a pitcher has control over, while tRA looks at the "quality" of batted balls given up. Both are summed up into nicely-packed numbers that resemble ERA (although one must multiply tRA by .92 to get tERA). In a mild attempt to see what happens when you mix two completely different statistics, I entered my laboratory and came up with a crazy concoction: TRX. It's literally just the average of each starting pitcher's xFIP plus tERA. Can one simply look at both stats in gauging a pitcher's performance? Sure, but isn't it more fun/interesting/easy to have one number? The sample size used is the the seventy-five starting pitchers that come up on Fangraphs for league leaders. Here are the results:
2009 Top 10 TRX
Tim Lincecum 2.74 Justin Verlander 2.92 Zack Greinke 3.03 Chris Carpenter 3.08 Javier Vazquez 3.10 Jon Lester 3.22 Felix Hernandez 3.24 Roy Halladay 3.24 Josh Johnson 3.27 Adam Wainwright 3.32
Nothing all too surprising, although Greinke a "distant" third in any ranking is odd, and we get to see how good Verlander really is. According to TRX, the bottom five pitchers in baseball last year were Jeremy Guthrie (worst), Braden Looper, Doug Davis, Trevor Cahill, and Kevin Millwood. I ultimately think this could be a nice quick-and-easy way to evaluate a pitcher for those who love DIPS theory, but also value knowing just how the ball came off the bat.
TRX has an R^2 value of .45 when compared with ERA (similarly, FIP has a .47 correlation and xFIP is .31, both based on the same seventy-five pitchers used).
trx.xls
Pat Andriola is a JD/MBA student at NYU. He likes the Mets a lot. You can contact him at .(JavaScript must be enabled to view this email address).
I already do this to evaluate pitchers, except I use tERA* and I add in qera as well.