This is an example of a defensive foul for blocking. To get into a legal position, the defender needs to establish himself in the path of the offensive player with the ball before contact is made, and BEFORE the offensive player starts his upward shooting motion. On this play, the defensive player initially establishes legal position in the path of the offensive player. But the offensive player then moves to his left on his field goal attempt and he “slips” by the legally established defender. At this point, the defender tries to re-establish his position and he leans to his right, initiating contact with the offensive player who is now in the act of shooting. Because of this late move by the defender, he is no longer considered to have a legal guarding position, and thus, this is a blocking foul.