I just think midfielders like Fellaini are ten a penny. When he's pushed up against the centrebacks, he's a good player, not a player I like watching, but productive. When playing deeper, sure, he's big and strong, but not particularly mobile, not a particularly good passer of the ball, and not particularly clever or tactically astute. I don't see what he'd offer us there that Alex Song, for example, didn't? Right down to the slow passing and lazy/poor tackling.