Screening the screener's defender turns a conservative pick and roll coverage into a choice between two outcomes the defence hates equally.
A backscreen on the big man broke the rulebook
For a long time the deep coverage was the closest thing basketball had to a safe answer. Keep the big near the rim, make the guard fight over the top, live with a mid range jumper. Then somebody put a screen on the retreating big himself, and safe stopped being safe.
The action is easy to describe. Standard ball screen on the wing. As the centre backs towards the paint, a third offensive player, usually whoever is guarded by the least reliable helper, sets a screen on him from behind. The big is now being asked to backpedal into a stationary body he cannot see. He fights through and arrives late, or he goes around and the roller has a straight line to the rim, or the defence switches and a guard is left trying to box out a centre.
What I like about it as a piece of design is that it attacks the coverage rather than the personnel. Most counters hunt the weak defender. This one punishes the strong one. The better your rim protector, the more committed he is to that retreat, and the more the screen behind him hurts.
Every defensive answer is uncomfortable. Pre switch the screener before contact, which needs two players to talk through crowd noise while both are watching the ball. Jump the big out to the level and refuse to be a stationary target, which gives up the pocket pass. Or tag the backscreener early with the low man, which by definition opens the corner you were trying to protect in the first place.
None of it is free, and that is the whole point. Good design does not manufacture an open shot. It manufactures a decision where every branch costs something, taken by a defender with a third of a second and eighteen thousand people shouting at him.
The version I would run more often is the fake. Show the screen, never set it, and let the big react to a threat that does not arrive. He hesitates for a beat. A beat is a layup.
Whoever first drew this up understood something coaches say far too rarely, which is that the most vulnerable man in any scheme is usually the one doing exactly what he was told to do.

