He has to be a fullback and he has to stay there to develop.
He cannot play CB mostly because he cannot win aerial duels, I think Per Krøldrup was better in the air. It is a shame as he has a terrific physical makeup for a holding CM but I don't think he has enough experience/positional sense, discipline to play that since he has not played in that spot regularly for a long time.
With that being said, he has the pace and strength that no one else on the team possesses. We need his recovery pace and his intensity. Like most of our defenders, he will make a mistake, a lapse in concentration, but it will be less damaging on the wing rather than in middle.