He's been a solid contributor to the team and does the team credit. But he gains nothing (and neither does ND in the long run) by staying to play another year a 6th year. The attributes that make him a solid game manager in college just won't translate well to the pro game.
The most optimistic outlook would paint him as a pro game manager who can serve a Chase Daniels type long term backup. But he isn't even Chase Daniels. While he looks mobile within the college game, he doesn't have pro level mobility to offset his below average arm (by pro standards). No pro defense is going to worry for 3 seconds about his "mobility." He gets away with his arm because he is playing against college dbs and defenses. While he occasionally goes on hot streaks, his accuracy continues to be below average with the ball frequently reaching receivers late. In the pros, that results in interceptions and wrs getting their asses kicked.
Long story short: free agent who will see a pro camp but will never play in a pro game that counts.