I'm glad Marshall has confidence in himself enough to believe he'll play in the NFL, but if Blake Sims was at AU, they'd have a quarterback controversy on their hands. Marshall is a system QB, he cannot make multiple reads and his accuracy on most of his throws beyond 8-10 yards is scattershot -- which is two-thirds of a pro playbook. Unless an NFL team decides to try to run zone-option as a base, I don't see him playing QB at the next level. I do expect some team will take him just to see if they can do anything with him, though.
Malzahn doesn't want him working with a QB coach because it's just not needed for their offense. However, as defenses continue to figure out his system, and especially if/when the NCAA changes its clock rules, he's going to need more than a glorified RB under center, which is what Marshall is.