Clay Buchholz was .06 points from an ERA crown in 2010, which is why his more normal (but still above average) 3.48 ERA disappointed in his 2011 injury-shortened season. In 2012, the Cy Young candidate Buchholz was completely gone: he had his first full season that was below average (measured by his 95 ERA+). This year, Buchholz leads the league in ERA and sports a perfect 9-0 record. How is one supposed to track his inconsistent career?
The first thing to note is that Buchholz has generally outpitched his FIP by a little less than one run. In 2010, he was lucky and outpitched his numbers by more than 1 run, and in 2012 he was unlucky and barely had a better FIP than ERA. Buchholz’s ERA in relation to his xFIP, however, has been all over the place. His ERA even exceeded his xFIP in 2012. As with anytime FIP and xFIP send different messages, the culprit is a radically fluctuating HR/FB rate.
Credit this year’s dramatic dip in xFIP is due to a much-increased K%; Buchholz’s BB% and flyball % have stayed fairly consistent over the last four years.
Buchholz’s xFIP implies that some more flyballs will surely leave the park, but his K% has been so good that his xFIP plummeted anyway. Why is Buchholz missing so many more bats than ever before? First, let’s look at his pitch selection (note that cutters are also counted as fastballs so the sum of his four main pitches’ percentages is greater than 100% each year).
Since his cutter use has changed the most, let’s start there. Hitters are certainly struggling mightily against it, but without an obvious statistical reason. His cutter whiff rate is continuing a three-year downward trend; his groundball rate with the cutter is a career low; he’s throwing almost the same number of strikes with it, and he has lost significant velocity from 2010.
There may be something to be gleaned from a more detailed analysis of Buchholz’s control. He has been placing more cutters low, but that’s good insofar as it tends to induce more groundballs, which has not happened for Buchholz. This year’s whiff and groundball rates low in the zone are closest to his 2011 numbers, which was his worst year of the four in terms of batting average and slugging.
There seems to be no choice but to call Buchholz’s success with the cutter a statistical anomaly that will fade, but examining his non-cutter fastballs yields results that Redsox fans will like better. His control is better than it was even in his 2010 campaign; this year’s whiff rate is a career high and more than double last year’s, and he has shown last year’s groundball % drop off to be an anomaly. The one concern is the nearly 2 mph that he lost off his fastball, but he’s lost the same amount off his changeup since 2010, keeping the difference between the two pitches constant. (His curveball velocity has also dropped a bit, giving Buchholz a second pitch that speeds up his fastball.)
No one needs to be told that Buchholz will not sustain his 4% HR/FB rate, that his ERA will rise as soon as his luck regresses to the mean, and that it is unlikely that he will finish the year holding opponents to a .147 slugging on cutters, especially if he can’t get more groundballs or whiffs. But since his 2010 breakout season, his fastball has gotten more called strikes, more swinging strikes, and the same amount of groundballs. If these trends continue—and there is no reason to doubt that they will, at least with his control and groundball rate—Buchholz will be poised to exceed his 2010 WHIP (1.20) and Cy Young finish (sixth), and perhaps even take a run at his career-best 2.33 ERA.