Layer 4 is NOT about Dribble Penetration. You can dribble penetrate at any time in any offense. But that usually means the end of the offense.
Layer 4 in the Read & React is about how the offense continues if Dribble Penetration fails or Penetrate, Draw the Defense, and Pass does not produce a shot.
I don’t think most understand WHY we Circle Move on Dribble Penetration in the Read & React. Here’s why:
Elementary Reason: Receivers moving vs standing are harder to guard.
Advanced Reason: Defensive help and rotation moves in the opposite direction as Circle Movement.
Engineering Reason: What if the drive fails or what if the drive and pass fails to produce a scoring opportunity? The reason to Circle Move is to continue action with another Layer of the R&R if the drive fails. That requires everyone to be on SPOTS. (All layers START on spots and END on spots in order to have continuous linkage of layers or basketball actions.)
When I was first engineering the Read & React (8 years ago), we did not Circle Move when someone Dribble Penetrated. That produced a problem: The empty spot from where penetration occurred was being filled by the next player (due to the habit of Layer 1) and the spot behind the filler was being filled, etc. That meant some were moving on the perimeter while others were not. The spots that were not being filled were the highest percentage passing windows (the Natural Pitches). My solution was to require EVERYONE on the perimeter to move one spot in the direction of the drive: REACTORS (those without the ball) have one reaction for one read – this would be consistent with the design of Read & React.
Again, the spot left empty by the dribble penetrator is going to be filled because of Layer 1. So, training the habit of moving one spot in the direction of the penetration is mostly directed at those in the Natural Pitch direction – usually only one or two players. The Safety Valve is going to be filled thanks to Layer 1!
The icing on the cake of Circle Movement is: if everyone moves one spot, then the penetrator has an empty spot in which he/she can “bounce off” into in case their drive fails. (It’s the spot vacated by the Natural Pitch.) This allowed penetrators to choose a better option if their drive failed (rather than pick up the ball, make a bad pass, or force a bad shot. This allows the action to START on spots and END on spots – if the drive fails. From there, any new action can be chosen and our flow of attack can continue.