I can see from much farther away that he's nothing special skill-wise. A good player, for sure, but no magician out there.
I don't know why people are saying he's not Barcelona quality. Not every player on Barcelona is what would be considered as Barcelona quality, and thats the same for Bayern Munich, Real Madrid, Chelsea and other top clubs in Europe. If Pizarro can play for Bayern Munich, Chicharito for Real Madrid, Ramires for Chelsea, etc. then Fabian Johnson can play for Barcelona. That doesn't mean they should be looking at him as plan "A" at their RB position, but he wouldn't be any more out of place than some other players that don't belong at the club either, in an ideal world. Yeah, if the whole team was players that are world class, then he'd probably be out of place at Barcelona, but there's not a team in the world who's whole squad is world class players or younger players with world class potential.
Beyond the "FJ deserves it" debate, is there any more evidence of Barca's interest than the one tweet?