Dictating the Action of the Ball. A player with the ball can do three things: He can release the ball with a shot or pass (which your bubble defense and hand position try to make difficult) or he can dribble to the right or to the left. It is intelligent to take two of these three options away and battle for the third.
Your bubble defense takes the shot and pass away. He may still shoot or pass, but either will be difficult, which is what defense is all about—making things difficult. That leaves the dribble to either side. So if you overplay to one side, forcing the man to go to his left or to the baseline or to a helping teammate, you take away a second option, leaving him just one opportunity to try to beat you in the direction you have dictated.
The advantage of this type of defense is that you don’t have to be prepared for anything and you don’t have to worry about fakes. You know what the player is going to do. Either he is going to take a bad shot, or he is going to have to make a good pass by your hand, or he is going to have to force the ball in a direction where he is already overplayed—unless he decides to try to beat you in the one thing you are prepared for.
By dictating the action in this way, you not only make it easier for yourself, but also you make it easier for your teammates. With the opportunity for your teammates to see in advance where the battle is going to be fought—where the ball is going to be taken, they have a better chance of getting into effective helping position.
From Dick’s book Stuff