Any self-respecting middle infielder would put you in the hospital with the velocity and distance that the situation provides. You slide for several reasons. Courtesy, since you're already out; self-preservation, because several instances this year have shown that baseballs meeting skulls is not a positive result for anybody; and tactical, because you're going to do a better job breaking up the DP by banging the infielder in the legs than you are by risking your life to get in his line of sight. Excellently put. Better than I could do. CubRock, While there is no rule that says you have to slide, there's no rule that says the infielder has to alter his throw to miss you if you're in the line of sight between him and first. So, if he throws directly to first but hits your noggin, he hasn't broken any rules. However, if you go out of your way to give him a forearm shiver like you so insinuated, you have broken a rule.