PD stands for pass or passes defended. For the stat to be recorded, the defender has to get his hands on the ball to disrupt the pass, either through a deflection or by knocking a nearly caught ball out of the receiver's grasp. The play must result in an incomplete pass. A deflected ball that is caught is recorded as either a reception or an interception, depending on which team caught the ball. PD's are used to assess a defender's performance but can also be used to judge a quarterback who makes poor decisions by throwing the ball into tight coverage by the defense.