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Wednesday, July 22, 2009

A note from a reader on BABIP

It has been some time now since the BABIP established its place in the sabermetric canon, and understandably so. BABIP means to aim a quantified scrutiny at a rather interesting problem: the extent to which a batter’s skill at directing 90 mile-per-hour pitches away from the best preventative efforts of sagely-positioned, gloved men can be assayed.

Yet, I have long experienced a measure of unease with the BABIP, and while my hermetic disquiet won’t suffice to give pause to a sabermetrician—and it shouldn’t—perhaps this simple example will:

Imagine two hitters, A and B, both of whom assemble 600 at-bats, 180 hits, and 100 strikeouts. A hits 15 home runs, however, while B musters 40. Both players hit .300, of course, but their respective BABIPs look like this:

A -- .340
B -- .304

And therein lays the conundrum. In what manner shape or form are we entitled to conclude, on the basis of the evidence placed before us, that it is A who more adeptly interposes batted balls between the defenders assigned to thwart him? How can we possibly formulate such a judgment when the data affords us no warrant to do so?

All we know is that B outhomers A, and all we have is a metric

(Hits-HR)/(AB-HR-SO+SF)

which falsely skews its conclusion. And that is because by informing both tiers of the fraction, the subtracted home runs pare the numerator artificially for power hitters, culminating in lower BABIPs.

Again - why should we be entitled to thus declare that high-home run achievers commit inferior skills to the challenge of turning balls in play into hits? That inference is simply not available to us.

In fact, BABIPs typically exceed players’ averages ; but for big power hitters, the relationship undergoes a curious inversion. Babe Ruth’s .342 lifetime average turns into a BABIP of .340. For Hank Aaron, the split stands at .305/.295; yet Rod Carew checks in at .328/.361. Can we thus assert, with the appropriate, straight-faced measure of confidence, that Carew’s ball-in-play facility truly overwhelms Aaron’s by 66 points?

The inarguable mathematical point is this: that, all other things being equal, the player with more home runs suffers a relative decrement in BABIP. All else is speculation. If we proceed from the eminently clear-eyed premise that home runs tend to be hit harder than the average ball in play, we can go on to propose that, were these fence-clearers to fall short by a few feet, they would nevertheless fall for hits in greater profusion than typical batted balls - thus resulting in a higher projected BABIP for power hitters.

That too qualifies as conjecture, albeit a sensible one. Still, the fact is that the BABIP puts the caliper to a most intriguing property of the batter’s skill set in a manner that doesn’t quite measure up.

And thanks for sharing my unease.


1 These figures omit sacrifice flies, which contribute a very small effect.

Cardinals ship out Duncan for Lugo for no apparent reason

This year, Lugo's offense has seen an uptick, hitting .284/.352/.367 in his best offensive display since his time with Tampa Bay in 2006 before being traded to the Los Angeles Dodgers at the deadline in 2006. However, his defense has become atrocious: he's checking in at a cool -43.2 UZR/150.

To put that in perspective, when Yuniesky Betancourt was traded to the Kansas City Royals last week, he was the consensus worst shortstop in the game according to many bloggers. His UZR/150 on the year? -17.4.

So far this year, Lugo is 11 defensive runs below average under John Dewan's plus/minus system. This is horrendous in 243 innings given the numbers rack up as the season goes on. The season leader in 2008 was Betancourt (there's that name again!) at 14 runs below average in 1,325 innings.

His ISO has sat well below .100 the past two seasons after never touching .105 or lower the rest of his major league career. His walk rates are still quite solid, same with his strikeout rates. His BABIP hit a rough spell in 2007 but has since bounced back fine. He hit a lot of grounders last season, and now he’s hitting a lot more fliners. Lugo’s tendency to hit a home run has all but vanished. He still makes contact, doesn’t swing out of zone, and he’s seeing fewer balls in the zone.

Duncan will be arbitration eligible after the year. Duncan burst on the scene in 2002, hitting 22 home runs in 280 at-bats for a line of .293/.363/.590. The year after, he bopped 21 homers in 375 at-bats for a .259/.354/.480 line.

It was downhill from there. He saw only 222 at-bats in 2008, hitting .248/.346/.365. In 2009, he drew the ire of Cardinals fans, hitting .227/.329/.358 in 260 at-bats before being optioned to Triple-A Memphis. That tends to happen when you're 1-for-31 since June 29.

Duncan's off-year notwithstanding, he provides an immediate boost to the Sox's hopes of hitting right-handed pitching: he has a career .270/.366/.485 line against right-handers. Let's not talk about his splits against left-handers.

Chris Duncan traded to the Red Sox for Julio Lugo; somewhere, Dave Duncan is punching a wall

That would hurt a lot more in Fenway (Icon/SMI)

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