I don't think it was the core wall itself creeping forward. I think his point was that we had a couple of players, who now need to be 2 yards away from the wall, that were being pushed out of their position by Chelsea players. As our players had to be 2 yards away from the wall, it should be impossible for the opposition players to interfere with them as they would have to be less than 10 yards from the ball to do so.