Reader Email: Phillies Great vs. LHP

Reader Nate sent in this interesting email:

I’ve been reading your blog for a few months now, and I really appreciate it as a way to stay on top of the Phils out here on the West Coast. I was randomly checking out some stats and found that the Phils have a mediocre 19-16 record against right-handed starters this year, but are a stellar 12-3 against lefties. I was really intrigued, so I looked up the team slash lines, and to my surprise, found they were almost identical: .246/.313/.366 against righties vs. .246/.313/.383 against lefties.

To me, there are two intriguing questions here: One, how is it that they have produced almost identically against RHP and LHP, given that the lineup is dominated by left-handed batters (or maybe that’s just the perception, since Utley and Brown, before this week, have been replaced by right-handed substitutes or platoons?)?

The second is that, assuming that the performance of our own starting rotation is unaffected by the handedness of the opposing pitcher (as far as I can tell, a reasonable assumption – there would be no reason to think our rotation would systematically underperform when opposed by right-handed pitchers, or vice versa), why should there be this vast gap in win percentage between facing LHP and RHP when the offensive production has been seemingly identical against the two? Is this just a case of small sample sizes and statistical noise? Is it that so many of the games have been decided in the late innings, when they have possibly been facing relief pitchers who are opposite-handed from the starters, that the starters’ handedness becomes irrelevant? Or is there something else at work here?

That is quite an interesting statistical find. I think it has an interesting explanation as well.

The Phillies score 4.0 runs per game on average against LHP; 3.9 against RHP. They allow 2.5 runs per game on average when an opposing LHSP is on the hill; 3.6 when an opposing RHSP is on the hill. It’s actually the Phillies’ pitching, not the offense, that is skewing the records.

In the 15 games against LHSP, the Phillies have used Roy Halladay 8 times; Cole Hamels 3 times; and Cliff Lee and Roy Oswalt twice. The Phillies have not used a #5 starter against a LHSP.

Even if it wasn’t the pitching, though, 15 games isn’t nearly enough to tell us anything about how the team fares against left- or right-handed pitchers. The data would be prone to far too much randomness, such as base-out sequencing and quality of opposition. The Phillies may have an .800 winning percentage against lefties, but given the small sample size, it is unlikely that that winning percentage represents their true talent.

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