One of the hidden reasons for the Royals' second-half surge has been Bruce Chen's work in the starting rotation. He basically opened the season as the club's No. 6 or 7 starter, but was pressed into duty around the All-Star break and has gone 5-3 with a 3.45 ERA, and that ERA is inflated by three particularly lousy outings.
Have you wondered how he's done it? I have. Grantland's Jonah Keri did more than wonder; he actually looked at a bunch of numbers and heat maps and his biorhythm charts and ... okay, I made up that last part. But I guarantee you that Jonah knows more about Chen's performance this season than anyone else. Including the Royals' front office.
Jonah's explanation for Chen's surprising success?
The facile answer is that he has been lucky. The league-average batting average on balls in play this season sits at .297, yet Chen has limited opponents to a tiny .229 BABIP as a starter, despite batters posting a healthy 20.7 percent line-drive rate against him. Batters have hit nearly twice as many fly balls as ground balls against him in those 13 starts, yet thanks to a low 6.6 percent home run–to–fly ball rate, just eight balls have left the park during Chen's time as a starter.
Dig a little deeper, though ...
Wait, before we dig a little deeper, can we pause to appreciate the facile answer, which quite often is the correct answer? As Jonah demonstrates, Chen seems to be making better pitches this season; the heat maps show that Chen has done a significantly better job of keeping his off-speed pitches away from the hitters' happy zones. But in the absence of some explanation for how he's done this, I'm inclined to chalk most of his improved numbers up to good fortune.
After all, Chen's strikeout-to-walk ratio this season (2.3) is essentially the same as his career mark (2.1). Chen's got that ridiculously low batting average allowed on balls in play, and by the way it was perfectly normal when he was pitching out of the bullpen, earlier this season. And while his Achilles heel has always been home runs -- giving up 1.5 homers per nine innings in his career -- he's actually just six home runs short this season of equally his career rate.
Six home runs. Fundamentally, that's the only statistical difference between Bruce Chen v.2013 and Bruce Chen Ten Team Journeyman Left Hander for Hire.
Earlier this season, I wondered if the Royals made a huge mistake in dropping Chen from the rotation in favor of Luis Mendoza and Wade Davis, both of whom weren't up to the job. If Bruce Chen had pitched in the rotation all season and pitched as well as he has lately, the Royals would be in line for a playoff spot.
That part is actually true. But there was no great reason to think, six months ago, that Bruce Chen was any better than Mendoza and Wade Davis. And I'm not sure there will be six months from now, either. Chen's basically a replacement-level pitcher who's having his best two months in a long, long time.
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