There are a few reasons why Clay Buchholz has outperformed his FIP and xFIP this season. He has been very lucky so far to currently have 10 wins and a 2.47 ERA. Coming into the season he had only Bill James and the fans projections on Fangraphs calling for an ERA under 4.00, but so far while his ERA has beat all the projections his strikeout rate continues to fall.
In the minors Buchholz showed an elite strikeout ability getting over 12 K/9 in Triple-A, but after his promotion in 2007 his numbers had started to drop. Even after a return to the minors to figure things out he only broke a 10 K/9 for a short stay in Double-A. His K/9 fell to 8.53 in a return to the majors in 2008 and while lower still showed a solid skill for the strikeout.
When he finally returned in 2009 to reach the majors for good his numbers took another hit. This time his K/9 fell to 6.65 last season and again this year to 6.13. It’s tough to argue though that a pitcher needs to get better when his ERA stands tied for third in the AL.
The first change that correlates with the falling strikeout rate is his pitch selection has gone from a largely fastball and curve selection to a fastball and slider selection. His changeup rate dropped slightly this season, but he still uses this a fair amount of the time.
It’s tough to use Pitch F/x for him since the data from his first two seasons is tough to use due to limited data as the system was setup. We can see from his other data though that he has made some changes since 2007. His velocity has increased on his fastball from 91 to almost 94 while his slider has increased from 82 to 89.
Normally a solid velocity increase would benefit his numbers, but perhaps his control has suffered. I can’t say there is any clear trend in his plate discipline numbers. While some go up and down there is no general trend to be seen.
This could be a good sign as he is just having some number variance, but while he continues to change his pitch selection we won’t know for sure. This and the potential for the trouble many of our pitchers are having with Victor Martinez behind the plate it’s tough to say where Buchholz will go from here. If he continues to pitch as he has so far this year his ERA will look more like the xFIP of 4.28 instead of the domination we have seen.