He wouldn't be able to play defensive midfield either, completely different positional sense required.He just isn't build to play as center back,he lacks many stuff for that position maybe he can be good defensive midfielder.I can't see him as center back on top level.
The problem with Barca is that Eric is actually really good against teams that Barca can pin back for most of the game, and many fans based on this were really rating him.
But it's not until you face teams that truly test you, and come at you, where you see how good a defender is, and this is where Eric's physicality will let him down. He's either not tall enough, fast enough, or strong enough. You need ATLEAST 1 of these 3 to be elite, but he is meh in all of them, that can only take you so far.