May 1, 2009

Prospectus Today

Pitching Diagnostics

by Joe Sheehan

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At any point in the season, pitchers will have a stretch in which their traditional stats, such as ERA or wins, don't completely match their underlying performance. When it happens at the start of the season, we can become excited or panicked about someone even though they're actually pitching much better than you might expect.

To find pitchers who have pitched better or worse than it appears they have, I've taken a look at three indicators in particular: line-drive percentage (LD%), batting average on balls in play (BABIP), and strikeout-to-unintentional walk ratio (K/UIBB). If a pitcher is giving up a lot of line drives but has an average or low BABIP, that's an indication that they're not pitching very well but getting lucky. The reverse—a low LD% and high BABIP, indicating bad luck—is also true. A pitcher's K/UIBB is a fundamental expression of how well they're controlling the strike zone, and can be used as additional information with the first two data points or on its own.

The following pitchers have been pretty fortunate so far:

• Paul Maholm. The Pirates' rotation was on the front page of ESPN.com's baseball website earlier this week, but you probably could have put a picture of their seven defenders up there instead. Maholm, a pitch-to-contact lefty, has a 3.09 ERA despite a 23.9 LD% and a 12/11 K/BB, and that's because the guys behind him have gobbled up everything. He's allowed a .267 BABIP, which is low for anyone, but incredibly so for a guy giving up this many ropes. There's nothing here to indicate that Maholm's ERA will end up below 4.00 this season.

• Braden Looper. The right-handed version of Maholm, Looper has a whopping LD% of 26.9 and a mediocre 16/11 K/BB, but just a .308 BABIP—league-average, but low for that line-drive percentage—and a 2.45 ERA. If all those acronyms and jargon seem a bit much, think of these guys this way: they're giving up a lot of hard-hit balls right at people. Since pitchers don't have the ability to guide the liners they allow into gloves, this is the kind of thing that doesn't last for long.

• Edinson Volquez. His ERA (4.45) wouldn't seem to qualify him for this kind of list, but when you look at his numbers, you find that he is giving up his share of line drives (21.1 percent) and is not paying for them (a .208 BABIP, third-lowest mark in MLB among pitchers with at least 20 IP). The biggest concern is that his command has taken a step backwards; he's walked 21 men in 28 1/3 innings (with 28 strikeouts). Volquez's stuff is so good that he's going to get his Ks; the concern is that his command, which was better but still not great last year, will force him to choose between missing the strike zone or throwing hittable strikes. So far, he's been fortunate, but that's not likely to continue.

• Johan Santana. You don't post a 1.10 ERA without some good fortune. Santana doesn't generate many ground balls, and has a 26.6 LD% but just a .274 BABIP. Santana's BABIPs will be low because he's a fly-ball pitcher—reflecting the simple fact that ground balls become hits in play more often than fly balls do—but that kind of line-drive rate eventually shows up in your ERA, even if you post better six strikeouts for every unintentional walk you allow. The numbers can go very low when the best pitcher in baseball catches some good fortune.

• Other very good pitchers benefitting from early-season breaks include Dan Haren (.214 BABIP, 20.5 LD%) and Matt Garza (.221 BABIP, 23.2 LD%).

On the other hand, there are pitchers who are doing a very good job at the things they can control, but seeing their ERA skyrocket nonetheless:

• Jake Peavy is pitching for a bad baseball team, one with lousy defensive range that plays home games in a cavern. That's how you end up striking out a man an inning, giving up a slightly above-average LD% of 19.1, and still allowing a .349 BABIP and a 5.49 ERA. The Padres are 14^th in the NL in Defensive Efficiency and 15^th in PADE, which means that Peavy is on his own this year... at least until he gets traded.

• I'm on record as saying that we've already seen the best year of Jon Lester's career. That doesn't mean I think he'll have an ERA approaching 6.00 this season, however. Lester has a 33/10 K/BB and a 20.9 LD%, which shouldn't produce a 5.88 ERA. Where it's gone wrong is on balls in play (.388 BABIP) and in his home-run rate. Lester has allowed homers on 18.8 percent of his fly balls allowed this year, the eighth-highest rate in the AL, and nearly twice his career rate. When those two numbers come down, as they will, Lester will once again look like a good starting pitcher.

• One of the limiting factors to the idea that pitchers don't have significant control over the results of balls in play is that the pitchers who allow worse results than usual on balls in play are weeded out in the minor leagues, or in short major league stints. At the bottom edge of MLB pitchers we may find guys who have high BABIP marks because they simply get hit that hard, rather than that they've been unlucky.

  I'll be curious to follow the progress of Adam Eaton's season in this regard. Eaton hasn't been effective since 2005 or good since maybe 2003, and this year he has a 21/7 K/UIBB ratio in 21 1/3 innings while allowing just a 15.7 LD% and a mere two homers. Despite all this, he has a .397 BABIP and a 7.17 ERA. Has Eaton been unlucky, or have his skills deteriorated to a point where he allows too many hits to stay in the majors?

As the season goes along, remember to look past the basic stats to gauge how a pitcher is throwing over a short period of time. What appears to be a stretch of ineffectiveness could just be bad luck, and a shutout streak could have as much to do with a run of atom balls as anything else. Line-drive rate, strikeout and walk rates, home runs per fly ball, and BABIP are all next-level indicators that get closer to true performance than ERA or wins do.

Joe Sheehan is an author of Baseball Prospectus. 
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