1. Make the defensive challenge more difficult by putting the midfield in recovering positions to help the back four. The back four can be patient when the ball is in midfield and keep their shape delaying the opponents until the midfield recover back to help.
2. Have a time limit before they can begin their recovery. Do the session with the four recovering midfielders first then make it more difficult and use only two recovering midfielders then just have the back four against the 8 attacking players and see how many goals the attacking team can score in an 8 v 4 overload situation in their favor.

Four Against Eight Overload Situation

1. Now we are really testing the back four players and seeing if they have grasped how to defend as a unit and how to decide when to mark a player and when to mark space in a 4 v 8 overload against.
2. Pay particular attention to the wide defenders being drawn to close down (C) or (D) and leave (A) and (B) free thus breaking up the shape of the back four unit and offering opportunities to the attacking team to get behind the defense in wide areas. Also observe the central players being drawn into midfield. Patience is the key here, let them play in midfield there is no danger there in this situation.
3. This is the best course of action where the back four stay intact and allow the midfielders of the attacking team to play and pass the ball in front of them.
4. They only attempt to close players down as they get closer to the goal or the ball gets closer to their immediate opponents. Here (C) gets the ball but is no danger and (2) holds position aware of where (C) is but moves across the field slightly closer to (A) just in case (A) receives the ball. 
5. If the ball is passed to (A) then (2) has to close (A) down. The rest of the back four move slightly across also, maintaining their distances.