Moving the Middle Infielders Towards the Hole: Part One

A couple months ago, I was tasked with examining the merits of a rather interesting idea. Nico asked Mike Gallego:

Do you play your middle infielders more to the hole when Cahill's pitching, because he fields his position well and has a good wingspan?

Every A's fan can tell you that Trevor Cahill is a great fielder on the mound—part of the reason his self-given nickname of Pterodactyl works so well is because of that huge reptilian wingspan that comes out of his delivery in a perfect position to field a batted ball. He led the American League in pitcher assists, with 54. And the Dewan +/- fielding metric gave Cahill +9 runs in 2010, the second highest figure in the majors among pitchers (behind Ricky Romero). But does that fielding prowess translate into something you can position fielders to?

I'm going to split this into two parts because of its length, with the second part running on Thursday.

First up? Determining if Trevor Cahill really is as good of a fielder as he looks. Or, more importantly for this, does he soak up more groundballs than most? If Nico's premise is true, that would mean that Cahill gets to a larger portion of the groundballs he generates than your average pitcher. Well, this was easy enough to test—I just took all of the qualified starting pitchers in 2010 and calculated their assist/groundball ratio. The following chart shows that assist/groundball ratio of every qualified starting pitcher in the majors, ranked in order, with Oakland's pitchers highlighted. Click to enlarge.

I know Cahill is a good fielder, but this just blew me away. Not only did he get to more groundballs than the average pitcher, he was the best in the league by leaps and bounds. But even crazier? Brett Anderson was second.

Now, even Brett Anderson would tell you that he's not exactly, how to put this, graceful out there on the mound. He doesn't have the agility or the glovework that Trevor does, and every scout in the league would agree. And yet, he ranked 2nd in the majors out of 95 pitchers in fielding groundballs. How is that possible? I have a guess: Fielding ability plays a factor, but more important is the quality of contact induced. Assist/groundball ratio would be a good proxy for pitcher fielding ability if and only if every groundball was the same. But if a pitcher had an ability to induce weaker contact than others, so that his groundballs were consistently softer than average? Then he'd have an easier time fielding grounders, and he would be able to get to more of them.

More on this later, as well as getting back to infielder positioning.