Lots on Alfredo Aceves
May 27th, 2011 by czar

FWIW, Aceves’ xERA before today was 4.71. He’s gotten very lucky — his BABIP was .190 — and his K/BB ratio was a very poor 1.4/1. So he probably is “a decent fill-in starter but not much more.”

This isn’t just a 2011 thing, his career BABIP is .230 and career xFIP is 4.41 It’s not really a matter of inducing a low BABIP either as his career xBABIP is .287. None of this is to say he’s useless, but he is due for regression in his stats at some point. His ERA for the rest of the season will probably be closer to 6.00 than 2.00.

In fact his current WHIP of 1.058 becomes 1.221 (xWHIP) if we assume a regression in BABIP to his xBABIP.

At what point is his chronically low BABIP sustainable?

Well, this isn’t even regression to a “standard” expected BABIP (some people use a flat .300), this is to an xBABIP that’s calculated based on his batted ball profiles, so unless he’s giving up “softer” line drives than most pitchers or directing his GB right at fielders there’s not a lot of wiggle room there. While it’s impressive that it’s (BABIP) been pretty low over his whole career, 148 IP is maybe 3/4 of a season for a decent SP. I am very confident in saying some regression is in order over, say, his next 150 IP. In addition, there is probably a bit of regression built into SP Aceves vs. RP Aceves.

None of this means he was a bad signing or is a bad pitcher, but people expecting a ~3.00 ERA going forward are probably way too optimistic. Mid 4′s seems about right, and his career xFIP agrees with that. Nothing at all wrong with league average production for a cheap contract.

So, it looks like a legitimate .226 BABIP helped by a little luck. A .226 BABIP is unsustainable only because no one is that good in the long run, but it’s been legitimate just as Crawford has legitimately been insanely good the last two games– none of those hits was remotely cheap.

This is very different than a guy with his same numbers where we can find, say, 8 lucky outs instead of 2. That would tell you that he’s not really capable of pitching that well for two months. But Aceves has shown that he is capable of being very nearly this good for this many consecutive innings.

I don’t think the best argument for Aceves regression is that his 2011 BABIP doesn’t match his 2011 xBABIP– my main concern is that he’s getting 8% of his BIP as LDs while his 2008-2010 seasons are 17%, 17%, are 20%.

I guess I just don’t see a tremendous amount of predictive value in saying “well, he wasn’t lucky via batted balls in 22 IP so far, ergo he’s a good pitcher.” First it’s a tremendously small sample size relative to his career burden and secondly you’ve proved he’s been only marginally lucky when those balls are in the air, but I’d argue that’s not the same as proving he’s hasn’t been lucky in the way that– say– 3 or 4 guys got just under a hanging curveball and sent them to CF instead of a liner up the middle for a base hit.

To me, saying he’s “capable of being this good” and projecting it forward would require similar stretches of this throughout his career (batted balls wise) of which there are none.

Posted in Message Board Ramblings


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  • Traversing the land that is known as Red Sox Nation, The Czar Who Wears Red Sox is an attempt at compiling a repertoire of my ever-so-sexy forum posts (when I'm too lazy to write my own damn entry) and other random baseball thoughts that strike. For those whose posts serve as the inspiration of my epiphanies and rants, do not be angry, but merely, be honored that you have achieved such status. Names will never be revealed. Feedback appreciated, as this is a work in progress.

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