I don't think he is a lone CDM material for this team. Playing lone CDM for Barca is very different than playing CDM for just about every other team out there. You must have positional awareness and ball interception ability without leaving your feet because you are the last and only line of defense infront of your CBs. Alongside that, you must also have the technical ability to initiate offense quickly and sharply.
Mascherano not only leaves his feet far too often for tackles, but he does not have the offensive sharpness to initiate quick play.