This drill not only teaches players how to play defense but to play offense also. Especially in the post.
First you divide the teams into three groups.Each group should be equal in both skill and quantity. Have each group space out around the arc with the coach in the middle. Next the coach takes a shot, make or miss the players in the front of the line battle for the rebound. Once a player gets it the other two play defense. The player with the ball has to try to score in the paint. The players keep playing until someone scores. Anything goes.
At least 3
Make so they can only score inside the 3 Point arc.
Post offense and defense. Also double teaming.
This basketball drill is licensed under a Creative Commons License. This drill is from Pål Degerstrøm at www.degerstrom.com/basketball.