All this talk lately about how Bruce Chen is a changed man has gotten me thinking maybe I should actually investigate this a little further. Supposedly he has a new or improved pitch, and McClure has tinkered with his delivery so it is now mostly a three-quarters delivery. So have the results changed or is this just a Small Sample Size?
Going to the quick and easy 2010 stats first, he has an ERA under 4, but does it deserve to be there?
ERA = 3.81
FIP = 4.58
xFIP = 5.02
So his numbers suggest that he should have an ERA higher by .77 runs. If Chen pitches 6 inning per start, his FIP is telling us he should have given up about a half run more per game than he did. And his xFIP looks even worse. It sure isn't the Royals defense saving Chen's ass, so let's come back to see if we can tell how he's doing it here in a minute.
But first, are these numbers better than Chen's career averages?
Career ERA = 4.66
Career FIP = 5.19
Career xFIP = 4.70 (but leaves out 4 early seasons in his career and more than 1/3 of his career IP)
ERA and FIP seem to suggest that he is indeed pitching better now, while xFIP isn't as good but has to be discounted because it is missing a large sample of his IP. So right now, Chen seems to have improved from previous seasons, by about .61 - .85 runs per game. I guess that takes you from out of baseball to #4/5 starter status.
Now let's see if we can explain the difference in ERA and FIP, and decide whether we think Chen's performance is sustainable. First off, Chen's HR rate is down 6.1% off his career averages, while he is giving up more flyballs. His K/9 rate is up by .33 over his career average, but his BB/9 is also up more than 1 over his career average! His BABIP is 35 points below his career average, and at .252 is kind of lucky, and we know that's not due to the Royals defense (John Dewan has them somewhere around the bottom for Defensive Runs Saved, if not last). If the BABIP number starts to rise, his ERA will likely look more like his FIP. And if his homerun rate goes back towards his average, his FIP will rise as well. These are all Red Flags of Doom to me. If his numbers regress to somewhere around his career averages or league average, he is in for one nasty second half. ZIPS Rest of Season projection agrees with me too with all of his stats regressing, and his ERA for the rest of the way being around 5.57.
So these 52 IP from Chen have been pretty good considering it wasn't expected. It's also a Small Sample Size as these 52 IP represent roughly 6% of his career. Do I expect his run/luck to continue? No. Does he have a new pitch and delivery that make him more effective? Possibly, but at this point, the league may just not have adjusted to it yet, or it could be completely luck. So what do I expect going forward? I expect a harsh return to reality very shortly where he once again looks like a fringe big leaguer at best, but I'd be very happy to be wrong.
C'mon Chen! Let's keep it going!