Sure, if we need him in the centre, play him there. But we didn't improve in that area when we made the change & we weakened the rb position.
Barca might have thought that about Mascherano at cb. But it became a way of getting more quality into the team. If Fernandinho got his shit together on the ball, he's a whole world better than most fullbacks we could find, who are usually deeply flawed & very expensive, some are slow & skillful, some are fast & shit, some are skillful fast & stupid, some can attack but not defend, etc etc.
There is no guarantee that the fulbacks we sign, will turn out better than the ones we have already. We just hope they will.
Having players who can solve potential problems is a godsend & is what Pellegrini should have been doing with the squad, & the kids, for 3 years.
I don't mind either way, but I'm sure Fern can learn that role & probably be as good as anyone else, is my point.