Trevor Cahill's Magical Sinker

The Oakland A's come to Wrigley Field for a three-game inter-league set. Former middle reliever Carlos Zambrano gets the start against righty Trevor Cahill. Cahill is a 22-year old sophomore who has a total of 41 big league starts under his belt. His calling card is a ground ball inducing sinker, and it's been working like a charm.

Cahill is throwing a few more four-seam fastballs in 2010, so his two-seam sinker is no longer the majority offering. It's still accounted for 43% of his pitches so far. He tops out just at 95 mph, averaging 90 or 91 with the sinker and 92 with the heater.

Cahill goes off-speed at least three different ways. He has at least one change-up, a rarely thrown straight-change and his more typical tumbler, that moves a bit like some splitters. Whatever they are, he throws them around 80-82 mph. He clearly has two breaking pitches, an 83-84 mph slider and a upper-70s knuckle/spike curve.

On the whole, Cahill is a well above average ground ball pitcher. Most of the action the A's infielders see comes off of Cahill's sinker and change-up. Both offerings have posted mid-to-upper-50s ground ball rates in 2009 and 2010, contributing to his overall rate of 48%.

The key to Cahill's success in 2010 has been turning ground balls into outs. I know, that's supposedly not a skill, but, well, take this for what it is.

In 2009 opponents had a batting average of .191 on ground balls against Cahill. This was better than the MLB average (.236) and the A's team average (.253). So far in 2010, Cahill's grounders are yielding a batting average of just .093. The league is at .228 and the A's are vastly improved at .194 (2nd in the baseball).

Cahill's success has been a function of luck, skill and quality defense. How much of each is unclear, but he won't keep this up. Still, I'd expect him to be better than average until proven otherwise. Or until HITf/x comes out.