Platoon Splits, BABIP, and HR/FB rates

The mention of Jered Weaver‘s platoon splits yesterday raised a few questions, with both Eric Van and Jeremy Greenhouse speculating that his arm slot could be the cause of his ability to limit hits on balls in play and home runs on fly balls versus right-handed hitters. In his career, RHBs have only racked up a 5.6% HR/FB and a .282 BABIP against Weaver, though he’s basically average in both of these categories against LHBs.

Putting Weaver aside for a second, I think the issue of whether or not BABIP and HR/FB rates are affected by handedness is worth thinking about. We know that certain pitches exhibit large platoon splits in walk rates, strikeout rates, and groundball rates – the two-seam fastball isn’t nearly as effective against opposite handed hitters, for instance. It’s essentially a totally different pitch to an LHB than an RHB. Does this carry over to things that we’ve presumed are not repeatable skills overall, such as HR/FB and BABIP?

This isn’t a conclusive study by any means, but I thought I’d start digging into it a bit. To begin, I asked David for the league average splits by handedness, 2002 to 2009, which I’ll present below.

RHB vs RHP: 44% GB%, 36% FB%, 12% IFFB%, .296 BABIP, 10.3% HR/FB
RHB vs LHP: 42% GB%, 38% GB%, 11% IFFB%, .303 BABIP, 10.5% HR/FB

LHB vs LHP: 46% GB%, 34% FB%, 11% IFFB%, .298 BABIP, 10.4% HR/FB
LHB vs RHP: 44% GB%, 35% FB%, 9% IFFB%, .306 BABIP, 10.9% HR/FB

You’ll notice that there is an average platoon split for BABIP, though its small – 7 or 8 points. There’s not really any significant HR/FB platoon split, at least in the aggregate. Despite the big platoon splits that are exhibited in things like strikeout rate, those don’t appear to carry over to BABIP or HR/FB rates.

Of course, the original question wasn’t whether all pitchers are able to suppress these two “luck” statistics against same handed hitters, but whether a pitcher with a certain type of arm angle could generate an advantage and beat the averages. Weaver is one example of a pitcher whose career data suggest that he may be able to, but we’re talking just over 300 innings against right-handers in his career, so the samples are too small to draw any firm conclusions.

So I went looking for other examples, based on similarly strange arm angled pitchers. Here’s the guys I chose to look up, based on my experience with watching them add some deception to their delivery with frequency:

Orlando Hernandez:

Vs LHB: .289 BABIP, 11% HR/FB
Vs RHB: .275 BABIP, 9% HR/FB

Vicente Padilla:

Vs LHB: .324 BABIP, 12% HR/FB
Vs RHB: .273 BABIP, 10% HR/FB

Bronson Arroyo:

Vs LHB: .298 BABIP, 12% HR/FB
Vs RHB: .291 BABIP, 8% HR/FB

Brian Fuentes:

Vs RHB: .294 BABIP, 9% HR/FB
Vs LHB: .324 BABIP, 7% HR/FB

Sean Green:

Vs LHB: .299 BABIP, 10% HR/FB
Vs RHB: .332 BABIP, 6% HR/FB

It’s only five pitchers, and guys like Arroyo and Padilla don’t pitch exclusively from a Weaver-esque arm angle, but it’s still interesting to note that all five pitchers have lower HR/FB rates against same handed hitters than opposite handed hitters – even Fuentes and Green, who do not follow the BABIP prevention vs same handed hitter trend. Both of those guys give up significantly more hits on balls in play against same handed hitters, but still manage to hold down the rate of fly balls that head over the wall.

Additionally, we’ve observed that a decent amount of relief pitchers generally have lower HR/FB rates than starting pitchers. Given that relievers face same handed hitters with more frequency than starters, this also points to there being certain types of pitchers who can sustain a platoon split on HR/FB rate.

This is nowhere near an exhaustive study, but the results are interesting enough that we should keep digging.

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Dave is the Managing Editor of FanGraphs.

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Any data on LD rate?