Jered Weaver and Splits

So, we have splits now. We’ve talked about how to use them and how not to use them. Today, I want to talk about why our splits matter. After all, Baseball-Reference has a great splits section, and has for a while. But, B-R is focused on providing factual data (which they do very well – this is no knock on the site that Sean has built), and as we’ve talked about before, sometimes what actually happened is not the best predictor of what is going to happen.

Let’s use an example of why having split data for metrics like xFIP is important. If you go to Jered Weaver‘s page at Baseball Reference, you’ll notice his career L/R split is pretty large. Righties have hit just .232/.283/.365 against him, but lefties have managed a significantly better .267/.327/.449 mark. There’s a 126 point gap between his OPS against RHB and LHB.

Now, look at Weaver’s splits page here.

Vs Left: 7.17 K/9, 3.01 BB/9, 36% GB%, 4.51 xFIP
Vs Right: 7.47 K/9, 2.30 BB/9, 28% GB%, 4.42 xFIP

That’s a pretty different story. In terms of the numbers that measure skills, Weaver’s not actually all that much better against RHBs than LHBs. The things that drive Weaver’s large career platoon split? HR/FB and BABIP, two of the least predictive metrics out there.

For his career, lefties have turned 10.6% of their flyballs off of Weaver into home runs. Right-handers have just managed 5.6%, causing a big gap in home run rate. Also, lefties have tagged him for a .307 BABIP, compared to just .282 for righties.

Maybe more research into these issues will reveal that handedness effects these two metrics more than we currently know, but right now, Weaver’s profile is not that of a guy who will continue to post big splits going forward. He’s no Vicente Padilla. He’s a little bit better against right-handed batters, but not much more than the norm.

You’d have a really hard time knowing that from his results. This is one of the great things that we’ll be able to flush out with split data here on the site, and one of the reasons we’re so excited to have them now.

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Dave is a co-founder of and contributes to the Wall Street Journal.

14 Responses to “Jered Weaver and Splits”

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  1. Mike Emeigh says:


    The higher GB rate by LHB is significant, likely explaining much if not all of the in-play BA differential, and possibly also giving a clue to the reason behind the large splits. Ground balls hit against FB pitchers tend to go for hits more often than do GB hit against GB pitchers (as do FB against GB pitchers, for that matter). Although I think more research is needed, I take that as an indicator of better, more consistently solid contact by LHB against Weaver – providing a potential explanation for the HR/FB rate as well.

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  2. AK707 says:

    That, and when LHB hit GB’s, they get a head start out of the box compared to RHB (their swing takes them to 1B anyways), hopefully turning in a higher BABIP. I haven’t timed it myself, but I know that there is a significant difference between the two.

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    • Travis L says:

      How do you know? While I’ve heard this theory as well, I’ve also heard the theory that a normal swing by a player generally takes them *across* the plate, thus conferring an advantage to the right handed hitter. In order for a lefty to have an advantage you can see, he would have to look like Ichiro, who clearly is heading to first as he hits the ball. But regular lefties don’t have the same swing finish profile, so i don’t think this issue is settled.

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  3. B says:

    Great issue, we’re definitely only scratching the surface here in terms of what we know from this data. Would be really interesting to see further research into it.

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  4. Nate says:

    Just a quick head’s up.. you have a link to his “slits” page, instead of his “splits” page. The link is good, just the text for it that’s got the typo.

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  5. AK707 says:

    I wonder if weaver also induces LH GB’s to the left side more? Forcing hitters to go the other way to put balls in play maybe?

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  6. drew says:

    Felix has similar issues to Weaver’s. Higher HR rate and BABIP in his righty/lefty splits.

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  7. drew says:

    Speaking of HR/FB being one of least predictive metrics out there…

    Check out the differences in Beckett’s 05 and 06 season (when he moved from the NL to AL).

    His HR/FB rate when pitching away from Fenway blew up from .92 to 2.27.

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  8. PhD Brian says:

    Could the quality of his defenders at certain positions during his career cause the much bigger real numbers? In other words, if he had a gold glover at third but an inept firstbasemen, then lefty and righty pull hitters where hitting into different situations and might see much bigger differences.

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  9. Eric M. Van says:

    Weaver may be the worst possible example, seeing he’s the only pitcher in all of MLB that I’m willing (based on pitch/fx data) to argue has a true BABIP skill.

    He has an unusual motion in that the upper arm is very much three-quarters but the forearm is vertical, resulting in a large rise and a small armside run, similar to a pitcher that comes right over the top (e.g., Okajima), whereas everyone else with his upper arm angle has the opposite. I believe batters unconsciously read the expected pitch movement from the upper arm angle and thus tend to be get under the ball and get it towards the end of the bat (if RH). The result is a lot of easy FB, especially to RF — a really high rate given the low % of swings and misses. The big platoon split comes from simply throwing the FB less often to LHB (perhaps for no good reason).

    This hypothesis would lead you to expect that he’d have a larger-than-usual split by times around the batting order (as batters acclimated to the deception), and in fact he does.

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    • Dave Cameron says:

      I don’t think the evidence supports your theory.

      Weaver, BABIP vs RHBs, career:

      2006: .219
      2007: .316
      2008: .339
      2009: .242

      If there’s a repeatable skill there, I don’t see it. And, of course, I’m sure you won’t argue that he has a repeatable skill of BABIP prevention against LHB, considering the .307 career mark he’s amassed against them.

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  10. Alireza says:

    Just looking at the mechanics of the Weaver Brothers, you would think they are going to be more successful against RHB. The ability to go submarine to throw that slider against a RHB would suggest more success.

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