Good coaches push basketball defenses that center around man to man defense, and for a good reason - every defense, whether man to man, or zone, or a combination defense, or a press, or whatever, requires strong man to man defensive basketball skills.
But basketball is a team sport, and we can't forget that - having excellent individual skills is only half the battle for our players (and for us, their coaches!). Our players need to be able to play hard defense on the man they are guarding, but they also need to be able to see what is happening on the rest of the court, so if one of their teammates gets beaten, they can help out.
The focus of defense is not to stop your man - it's to stop the ball, and sometimes that's going to mean leaving their own man to stop someone else's man who is penetrating. So it's important that we teach our players how to help out and recover.
Basketball Defenses: Help and Recover
The focus of a defensive player when trying to help a teammate that has been beaten is not to pick up the ballcarrier, but to make him think he is being picked up. We call this Help and Recover because the "help" portion is only half of it.
What has to happen may best be explained using a situation.
Let's say player #1 gets beaten, and his man drives past him on the way to the hoop
Player #2 is the closest defensive man, so he steps into the path of the driving ball carrier
Player #2 does not play defense on the ball carrier, but rather slows him down enough so that player #1 can get back into defensive position. Player #2 quickly gets back into position to pick up his own man (this is the "recover" part)
There are, of course, risks here - #2's man may cutback door when #2 steps in to pick up the ball carrier; the ball carrier may make a quick pass to #2's man while #2 is out of position, and #2's man can shoot. But the alternative is to allow the ball carrier to waltz right in to the hoop.