He's never looked anything special for the first team, not a top level player by any means.
He's not very quick, strong or creative so it'd be very difficult to find the right partner for him at a top club - you'd essentially be carrying a midget who can finish. Trying to find a partner that suits him wouldn't be so difficult at a lesser club - a Zamora, Llorente etc, - but there's no-one with that range of abilities with that much quality to go along with it, and trying to find a system to work with him is probably even harder.
His interplay looks good at Barca but who's wouldn't? Constant movement and constant service, it's a god-send. His hold-up play's fine for his size but again not great. The only thing top-level about him is his finishing and movement, and that's just not enough.
If he doesn't make it at Barca - and with their striking purchases over the last few years, it seems likely - he'll have a tough time making it with the best. He's been hyped up so much because of his first season that he'll always be a disappointment, I reckon.