Looking for a Buch(holz)

Clay Buchholz looks good. Clay Buchholz looks real good. Fans begin to wonder, “is this the Clay Buchholz we heard so much about in 2007?” Word is leaked that he is sore. No big deal, he’ll just skip a side session. Or a start. A few starts. OK, he’s on the disabled list. And now he’s dealing with some freak injury that no one can peg down. Welp, he’s missed half the season.

Sound familiar? If you are a Buchholz owner in a keeper or dynasty league, 2013 was the fourth year in a row where Buchholz hit the disabled list. The past three years, his injuries have been A) stress fracture to the L2 vertebra, B) esophagitis, and C) some sort of mysterious trapezius/neck/shoulder strain. When he was healthy, he was one of the best pitches in baseball, posting the lowest ERA among pitches with at least 100 innings and coming in 20th overall in our end-of-season cumulative FVAR rankings, even though he only tossed 108.1 frames.

While posting a low ERA is not new for Buchholz (his 2.33 ERA in 2010 was second in the American League behind Felix Hernandez), 2013 was different in that his SIERA and xFIP were both about three-quarters of a run lower than his career average coming into the season. There was some luck in posting a 1.74 ERA, but there were also tangible improvements in his peripherals as well.

For the third year in a row he managed to keep his BB% below 9%. In fact, even though his 2013 mark was a tick higher than 2012, Buchholz has continued on a fairly linear downward trajectory since he broke into the league (11.5% BB% during 2007-2008). Interestingly, this decline isn’t tremendously supported in plate discipline metrics. His Zone% remains approximately the same and his F-Strike% has bounced around more than his BB%. One interesting note is his O-Swing% roughly correlates with the decline in BB%. Perhaps some of his walk rate decrease is because batters are hacking at a few more pitches out of the zone.

So why would they be doing that? It could be because Buchholz’s stuff has become eminently more hittable and hitters want to take their chances. However, you’d expect this to manifest itself in his O-Contact, which held steady at 69% from 2010-2012 before dropping to 66% in 2013. So batters are swinging at pitches out of the strikezone and making less contact. Well, clearly we’ve just explained Buchholz’s improved strikeout rate! His K% jumped to levels that haven’t been seen since his rookie year in 2007. But wait, if Buchholz’s strikeouts were because of all these extra swings and misses, why didn’t his SwStr% improve by more than a percentage point?

We only find that answer once we break down how his strikeouts were recorded. The fraction of batters the Boston righty whiffed swinging (K_S%) remained similar to the numbers he has put up over the last few years. What has changed instead, is the fraction of batters caught looking at a Buchholz pitch. His looking strikeout percentage (K_L%) has climbed from 4% in 2011 to 6% in 2012 to 12% in 2013. In 2011 the fraction of his strikeouts that were called (K_L/K_Tot) was 25%. In 2013 it was 47%.

So is this a fluke, or did Buchholz add a new sustainable skill? It’s important to note that, while a pitcher’s swinging strikeout rate is more correlated year-to-year than looking strikeout rate, the latter is not far behind. Helping Buchholz’s case is that fact that he joined Jose Fernandez and Gerrit Cole as the only two pitchers in 2013 who had positive linear weights on four different pitches. The ability to throw multiple pitches well should help keep hitters off balance, but, perhaps more importantly, keep hitters from teeing off on Buchholz’s fastball when his secondary stuff is flat. If you were to envision a pitcher who had the power to post high K_L/K_S, he’d probably be like 2013 Buchholz; solid, but not elite, swinging strike rates, but above-average performance on a multitude of pitches with different velocities and break.

He won’t put up a 1.74 ERA again, but there is reason to believe his improvement this season wasn’t dumb luck. However, the key to his success may not be founded in having hitters swing through his curveball, but rather more at bats that end like this one: