Wednesday, March 06, 2013
Measuring BABIP skill
I studied a bunch of variables I thought might have something to do with hit suppression on balls in play. I came up with two — both FanGraphs stats — that seem to have significant predictive power. The first is pop up rate. The second is z-contact, which is when batters swing at a strike — balls in the strike zone — thrown by a pitcher. What percent of those times does the batter make contact? It turns out that, just like inducing pop ups, it reduces BABIP and correlates consistently year to year. Getting batters to swing and miss at your strikes has strong predictive power on hit suppression.
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I should correct this:
Tom Tango’s FIP assumes that all pitchers have exactly league-average BABIP ability.
Would someone suggest that OBP "assumes" that all times on base are created equally, that OBP "assumes" that a walk is worth the same as a HR? No. OBP is very clear: it is only interested in the NUMBER of times a batter reaches base and is AGNOSTIC as to how far he got. It takes no position on the QUALITY of reaching on base. OBP looks at the SUBSET of a hitter's performance.
Similarly, FIP? is also looking at the subset of a pitcher's performance (those that do not require his fielders be involved) and is agnostic on everything else about his performance. The difference is that FIP explains a pitcher's skill far more than OBP explains a hitter's skill, and so, we then get fooled into thinking that FIP is saying that a pitcher has no skill on balls in play. But, FIP is not saying that at all, and neither am I.