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He went the first 11 games of this year without allowing a round tripper after ending the 2008 season on a four-game homerless streak. That's about a half season of starts and proof that Greinke's ability to prevent homers was no fluke, right?
Judge for yourself by looking at Greinke's season since then. He's yielded 11 bombs in his last 15 starts, including one last night when he fanned 15 Indians.
Greinke's ERA sat at 1.10 through his first 11 starts. Since that homerless streak ended, his ERA has been 3.30 – good but more in line with March expectations. So was Greinke just lucky during that dead-ball stretch and has he merely regressed back to his mean since then?
When Voros McCracken invented DIPS (defense independent pitching statistics), one of the assumptions was that pitchers take full responsibility for homers allowed. While they're certainly not the fault of the defense, the implication was that homers are thus less random and more closely aligned with the hurler's true ability.
Let's test that assumption by looking beyond Greinke at the 2008 leaders and trailers in homer rate, that's the percentage of homers allowed on all fly balls. Then we'll see if they're faring similarly in 2009. Not a perfect test, of course, but reasonable.
The most homer-prone pitchers of 2008 who have also pitched enough innings this year to qualify for the leader board are John Lannon (17.5 percent homers on fly balls), Jeff Suppan(notes) (16.8 percent), John Lackey(notes) (16.6), Armando Galarraga (14.8) and Bronson Arroyo(notes) (14.5). Their rates this year are 10.8, 14.1, 9.8, 13.9 and 13.5 percent, respectively. In sum, three guys trending pretty much the same and two are down significantly to below the major league average (11.5 percent).
You certainly can't conclude that homer rates are not random from that, though it's not a convincing case either way.
Now let's look at how the least homer prone pitchers of 2008 are faring in 2009.
Cliff Lee(notes) was 6.0 percent last year and was 6.7 this year for Cleveland before moving to Philly, where he hasn't allowed a homer in 40 innings. Tim Lincecum(notes) has gone down from 6.5 to 5.7 percent. Ubaldo Jimenez(notes) has held steady (6.9 to 6.8), as has Mike Pelfrey(notes) (7.2 to 7.4). John Danks(notes) is still below average (7.1 to 9.4).
Based on two years worth of outlier data, I put more stock in the guys who limit homers at an extreme rate than I do in the guys who allow them to extremes. But that's not so unusual, as I'd be more confident that a guy who hit .340 is a superior hitter than the guy who hit .240 is an inferior one. In baseball, it's so much easier to stink than it is to be great. So being great always means more.
Let's look further at the homer data and make some recommendations. We're just about in September, the time of year when our focus shifts to next year's value board.
Chris Volstad(notes), Marlins: You can't legitimately go from 4.7 percent homers to 18.4 percent. Let's split the difference and call Volstad average at preventing homers. That means his ERA next year should be up to one run lower, call it 3.75-to-4.00 on the 2010 projection board.
Joba Chamberlain(notes), Yankees: His rate has more than doubled from last year. And exhaustive study by physicist and baseball aficionado Alan Nathan says that those fabled wind currents at the new Yankee Stadium have actually suppressed the distance traveled on fly balls by about two percent. The fence in right field is shorter though. But not short enough to cause this level of increase.
Zack Greinke, Royals: He's stingy with the homers, looking at three-year data. But he's not a huge outlier here. I'd expect 15-to-18 homers allowed next year and an ERA of about 3.00.
Jason Marquis(notes), Rockies: His homer rate allowed has gone down steadily since 2004. He's an extreme ground-ball pitcher. If he gets out of Colorado somehow, the numbers will improve because Coors is still an extreme run-friendly park.
Jarrod Washburn(notes), Tigers: Caveat emptor, Detroit. His homer rate was seven percent for the Mariners and is 25.3 percent for the Tigers, leading to a 6.04 ERA. He's what we all thought he was in March.
Michael Salfino's work has appeared in USA Today's Sports Weekly, RotoWire, dozens of newspapers nationwide and most recently throughout Comcast SportsNet, including SNY.tv, for which he also analyzes the Mets and Yankees. He's been writing "Baseball by the Numbers" weekly since 2005.