Many people have made the comment that he probably realisies its inefficient for him to run because he will be tracked constantly. It is different to being man marked where you can keep on the move making your marker tired and hope he loses concentration. He is now essentially marked by two centre backs and three centre midfielders they work as a team. Before he would run into space and the players would get confused as to who follows him, now in the middle they all work as a team and track him. It is essentially pointless, if you watch he is constantly looking around waiting to see if he is being tracked if he isnt he will make a few yard to dash into space.
As for closing down, he has never fully done it and doesn't really need to do it except in the big games. I would prefer him to walk around then get the ball and score a goal or make an assist than for him to run around trying to find space and closing down only to not contribute.