Defending the ball screen is a key to any defense, pros, college or high school. There are many different ways to defend the ball screen, but the key to all of them is communication. When the communication breaks down between the 2 defenders, that's exactly when you get burned by the offense. Watch the video and then you can read my thoughts below.

I wish I had paused the video midway so that you can see it clearly, but you can pause midway to see it for yourself. Bargnani's defender decides to stay underneath as he anticipates Calderon driving towards the baseline. Calderon's defender has no idea what Bargnani's defender has chosen to do and so he follows Calderon. After Bargnani sets the screen, Calderon decides not to use the screen seeing Bargnani's defender cheating underneath. He makes a quick dribble towards the baseline and when he sees the communication breakdown he feeds Bargnani who is wide open for the 3-pointer as diagrammed below,

You must teach your players to constantly communicate with each other. This is how teams get broken down defensively when they don't communicate with each other. Players end up blaming each other for missed assignments.

For more ideas on the pick and roll and how to defend it, take a look at Jeff Van Gundy's DVD on the pick and roll. Van Gundy goes through both executing and guarding the pick and roll. Also, I have a some Jeff Van Gundy and Stan Van Gundy notes that might be useful, check out the X's and O's Basketball Forum to check them out.