I believe he is improving or adjusting defensively in this position. Obviously he will never be a top DM like Cambiasso, but I think his defensive skills are no worse than other deep lying playmakers playing there, like Xabi Alonso, or Pirlo.
He got many good sliding tackles, and stole the ball on many occasions. He still misses here and there, and he would have to imporve on that, cause when someone skipps him, then there is a big hole in front of deffense, with nobody to close down. That was the case yesterday, but it happened just 2, 3 times. He also has sometimes his "brain issues", although good thing, they are not as sever as with headless. If he improved on that, and on his defensive skills(especialy mental ones) I think he would be amazing in that position for us(considering it would stay that way).