I would love to see Denard in the NFL, but I just don't see a long career for him. People hit hard in the league, and he's injury prone.
He can't catch, and as a DB, it would be quiet a learning curve, which would put him a year or two behind. Not worth a top 5 round pick.
As a returner, he'd get hurt and not have value. Maybe as a specialty back on pitches and tosses to get to the corner, but even then the injury thing pops back up.