Managers play the platoon advantage as often as they can. With a right-handed starter on the mound, the opposing manager will look to play his lefty hitters, to the extent that he has that flexibility. Additionally, every bullpen features at least one lefty specialist whose sole purpsose is to enter the game in the late innings to face a particularly menacing left-handed slugger.

Why go to so much effort? As has been demonstrated for quite some time, hitters fare much better when facing opposite-handed pitchers. In 2010, right-handed pitchers allowed a .710 On-base Plus Slugging (OPS) when facing righty batters, but a .750 OPS when facing left-handed batters. The split is reversed for lefty pitchers.

Why such a big difference? There are a lot of possible factors. Arm angles have something to do with it. The break of the ball also does. Is it harder for a hitter to hit a breaking ball that's coming at him and breaks away from him than one that starts away from him and breaks in? Some say yes, some say no.

We put together the charts below to see how often pitchers throw their breaking ball against righty and lefty batters. What we found is this: pitchers who throw sliders will use it against same side hitters, but will substitute the change-up when facing a hitter from the opposite side.

The surprising part was the curveball. We expected the same trend for the curve, but pitchers throw curves, in aggregate, the same amount regardless of which side of the plate the hitter stands.