One reason for Roy Oswalt's success is his command of the curve ball. Over the last three years, batter found it difficult to square up, as they managed a meager .252 BABIP against Roy on the pitch. That puts him in the 83 percentile among pitchers in that time. Why is his curve ball so difficult to hit?
First, Roy offers consistent movement:
That nice big red zone indicates Roy can put Uncle Charlie in the intended spot. Against right-handed batters, that almost always away and low:
The pitch sweeps away from the righties, and they end up striking out in 37% of the plate appearances that end on the pitch. When a batter has a tough time making contact with a pitch, he's unlikely to hit it hard when he does make contact. That makes it easier to turn into an out.
With left-handed batters, Roy takes a different approach with the same pitch:
Roy uses more of the strikes zone against lefties. Given the platoon advantage, lefties get a better look at the pitch, so Roy keeps them guessing where it will be in the strike zone. Lefties only strike out 29.5% of the time on the pitch, but do no better when they put it in play. Note that Roy does a good job of avoiding the hanging pitch. When he's inside to lefties, it's almost always low.