Monday, September 6, 2010
Phil Hughes and his Home Field Disadvantage
Phil Hughes stormed out of the gate this season, winning 10 of his first 11 decisions and putting up an RA of 3.17 through through his first 13 games. Opposing batters hit .224/.281/.329 over that stretch.
However, hidden in those first 13 starts was something that’s starting to become more and more apparent, and that was the fact that Hughes has not pitched as well at home as he had on the road.
FB%: Percentage of batted balls that were fly balls
GB%: Percentage of batted balls that were ground balls
LD%: Percentage of batted balls that were line drives
HR/FB: Percentage of fly balls that were home runs
BABIP: Batting average on balls in play
FIP: Fielding-independent pitching
xFIP: FIP using league average HR/FB rate
Stk%: Percentage of pitchers that were strikes
BB/BF: Percentage of batters faced who walked
K/BF: Percentage of batters who struck out
Hughes’s batted ball types against and other peripherals were pretty consistent home and away, but at home he’d given up all seven of the home runs he’d allowed to this point. Because of that, the disparity between his home and road FIP was pretty large. If we adjust for the big difference in his HR/FB rate by using xFIP, which substitutes the league average rate of 11.1% HR/FB for actual HRs allowed and regresses BABIP to league average, the gap between his home and road performance narrows quite a bit.
So although there was a big difference in his results to this point, it wasn’t necessarily really indicative of anything other than small sample size fluctuation.
Unfortunately, since then Hughes’s performance has fallen off markedly.
Hughes has been much worse overall since then, but his performance at home has gotten even worse. He’s allowed both a higher rate of fly balls combined with a higher than average rate of HR/FB. Suffice it to say, that’s a combination that is not conducive to success. His road HR/FB has corrected to be closer towards league average as well, although you can still see the gap in his peformance if you look at his FIP and xFIP.
As far as why this is happening, I have no idea. Is he tiring? Has the league adjusted to him? Are his mechanics out of wack? It could be any of these things in addition to multitudes of others. Possibly all of them in some sort of combination.
In the big picture, we need to look at everything Hughes has done this year, because that tells us more than two samples chosen using selective endpoints.
The difference in his batted ball types at home and on the road is not really statistically significant.
We shouldn’t necessarily think that Hughes has some kind of issue that prevents him from pitching well at home. Players do generally pitch better at home than on the road, so if anything we should probably expect that Hughes would do the same going forward unless we see more evidence that he can’t.
Still, I have to admit that the specter of Hughes starting in the postseason right now is not exactly one that fills me with warm fuzzies, if by some miracle the Yankees get there. But I wouldn’t rule out the possibility that he pitches well enough over the rest of the year to deserve the chance.