Coaches always tell their defensive players, “See your man and see the ball.” And that should tell you, if you want to get open on offense to go somewhere that your defender can not see you and the ball. Often, you can do this by ducking and leaning to your defender’s back side but hardly moving your feet. The advantage of ducking out of his sight is that you disorient him. You make him wonder momentarily if you have cut backdoor, and you get all his attention—and often his feet—going after you, and then you can react accordingly.
Players trying to get open to receive a pass too often jockey back and forth, working very hard but not really going anywhere. Although they think they are confusing the defender because they are faking one way, and the other way, and the other way, and the other way, the defender can guard them by merely standing still.
Choose to go backdoor or choose to come out for the ball. And just before you choose, ducking out of sight, disappearing low and behind your defender’s head will often get you free by several steps. It works simply because defenders are not accustomed to guarding someone who disappears! Either they lose sight of you, giving you the opportunity to thrust out while they are not prepared to move as you do, or they overcommit (thinking you’ve gone backdoor) and are badly faked out when instead you are suddenly coming out for the ball.
From Dick’s book Stuff