I don't know how anyone can call Casey's slide dirty. How was he supposed to know that Aybar was going to go back to touch the base? When a runner is breaking up a double play, he is looking at the base and the infielders legs, you assume that the infielder will catch the ball and hop over you. Casey slid directly over the base with no roll or popup. It was a textbook example of how you should cleanly break up a double play.