The primary question is, "how does he respond to NFL speed" In every interview I have seen, this is the first thing that slaps rooks in the face. Offenses are faster. Defenses are faster. Schemes are more complex. Reads and responses can be multi-faceted.
Can he get past that? I have no doubt. The question is, how fast can he get faster?
This was something that Jason Campbell was never able to overcome. The game just never "slowed down" for him.