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What We Talk About When We Talk About Darren O’Day’s Slider

The playoffs have a way of turning role players into celebrities. The playoffs also have a way of turning superstars into celebrities — it’s all about who performs at the right time over small samples — but the playoffs are a time for role players to capture extensive attention, and a guy who’s getting a lot of attention right now is side-arming Orioles reliever Darren O’Day. O’Day has been of tremendous value to the Orioles in 2012, and in this ALDS. Previously, he went undrafted out of college. The Mets grabbed him from the Angels in the Rule 5 draft. The Rangers grabbed him off waivers from the Mets. The Orioles grabbed him off waivers from the Rangers. O’Day’s always been valued enough to have a job, but not really enough to keep it for long.

One of the interesting things about O’Day — one of the things that’s made him valuable — is that, for a side-arming righty, he’s been surprisingly effective against left-handed hitters. Not just this series, not just this season, but over his career. Over 640 total plate appearances, righties facing O’Day have posted a .281 OBP. Over 364 total plate appearances, lefties facing O’Day have posted a .285 OBP. There are differences in average, slugging, and wOBA, as you’d expect, and it’s not like O’Day has an even platoon split, but he doesn’t have a giant platoon split, and that’s kind of weird for a guy with his arm angle.

I don’t need to go into great detail because just today our own Dave Cameron wrote about this. There are multiple reasons why O’Day is able to get lefties out, and a big one is that he likes to throw his four-seam fastball up in the zone, especially in two-strike counts. He pitches all over, and doesn’t try to live in the low-away quadrant, as others do. But O’Day also throws lefties a ton of sliders, especially early in the count. O’Day likes to use his slider to get ahead. We’ve been taught that sinker/slider guys tend to have big platoon splits if they don’t have functional changeups, yet O’Day’s an exception. It’s worth saying a little something about his slider.

And what’s worth saying is that Darren O’Day’s slider isn’t like just any other slider. I guess this isn’t so much about O’Day as it is about side-armers in general, but while we can classify their different pitches just like we can classify the pitches of more conventional throwers, the pitches aren’t the same. Because of the arm angle, they move differently, so a side-arm slider isn’t like a high-three-quarters slider. To group them all together under the same header is misleading.

This is a post from Matt Lentzner at THT from 2008 that explains what I’m talking about in detail. Lentzner breaks down how the different pitches move based on the arm slots from which they’re thrown, and clearly you can see that a side-arm slider behaves differently from what you’d expect when you hear the term “slider”. A side-arm slider moves more like an overhand cutter, and you know what’s an effective pitch against opposite-handed batters? The cutter. If you have a good one, anyway. Darren O’Day believes in his slider kind of a lot.

This is a visual comparison between a recent Darren O’Day slider to a lefty and a recent Joba Chamberlain slider to a lefty. O’Day and Chamberlain are two very different pitchers, but it might help to have moving images at your disposal.

It’s hard to identify movement on the fly, especially from an off-center camera angle, but O’Day’s slider is almost like a changeup that tails in the other direction. Where his fastball averages about 85, his slider averages about 78. Where his fastball averages a lot of sink and about six inches of movement in on righties, his slider averages a lot of sink and about six inches of movement in on lefties. It is, technically, a slider, in that it’s thrown like a slider, but O’Day’s arm angle simply changes the meaning of the classification.

It would be one thing if O’Day just threw a slider, but he happens to throw a good one that he trusts. The last two years, better than 70 percent of O’Day’s sliders thrown to lefties have gone for strikes. They’re seldom swung on and missed, but they’re frequently taken for strikes, because the arm angle is unfamiliar and the movement is unfamiliar too. O’Day has a pitch he can use to get ahead of lefties, and he has another pitch he can use to put lefties away. These are rare traits for a pitcher like him.

He isn’t completely unique. Joe Smith is another side-arming righty, and his career platoon splits fall short of being obscene. Smith has posted very similar strikeout rates against lefties and righties alike. Yet Smith’s slider isn’t the weapon against lefties that O’Day’s is. O’Day’s is a legitimate pitch for any count, and he pitches like he’s aware of it.

We’re all learning a lot about Darren O’Day these days, because he’s pitched well under some of the very brightest lights. One of the things we’re learning is that he’s effective against lefties, which is weird, and the explanation for that is complicated and fascinating. Darren O’Day throws the hell out of his slider to lefties and righties alike. In some ways, it’s just a slider, and in other ways, it very much is not at all.