Sarris: Is fouling off pitches a skill?

From SABR member Eno Sarris at on November 10, 2014:

Are foul balls a skill? Do they lead to better outcomes? Should all hitters have a two-strike approach? These are the kinds of things (among others) that Sam Fuld has been thinking about in the outfield.

Let’s try to answer some of those questions the best we can.

If fouling a ball off was an easily measured skill — if percentage of balls fouled was a good measure of that skill at least — then you’d expect the skill to show through most years. Strikeout rate, for example, is fairly decent at measuring your ability to make contact. Strikeout rate stays fairly stable — you could use shorthand to say that almost 90 percent of your strikeout rate next year is described by your strikeout this year.

Foul percentage doesn’t work that way. Your foul percentage this year describes about 40 percent of the variance in your foul percentage next year. That makes foul percentage more unstable than batting average, batting average on balls in play, or your rate of doubles per plate appearance. Brian Roberts was 11th in baseball foul percentage this year, he was barely above average in 2013. So it goes.

If you up the minimum number of pitches seen from 300 to 1000, you finally push the year-to-year correlation past 50 percent. So, once you look at players over that threshold, you can see that Pablo Sandoval was No. 1 in foul percentage this year — he fouled off 26 percent of the pitches he saw — and also in 2013, when he fouled off 25 percent of the balls he saw. (Second in 2012.) Still not as “sticky” as on-base percentage when seen as a whole, and just barely better than batting average.

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Originally published: November 10, 2014. Last Updated: November 10, 2014.