Unless you're an NFL scout yourself, you probably don't have any idea what NFL scouts are looking for. That isn't to say that I do either necessarily, but I do know this: the NFL drafts on future potential almost as much if not more than they do on present achievements. It's why guys who played junior varsity league competition in college like Blake Bortles and Dri Archer can still get drafted so high as opposed to proven, battle-tested commodities like Connor Shaw, Aaron Murray, etc.
Justin hasn't proved a whole lot in college, but there's some things to like about his game. For starters, at 6'4 and 225, he's a big boy. That's NFL-ready size right there. He's also an intelligent, mature, likable kid and a good leader in the locker room. If he can impress in chalkboard X&O sessions and in team interviews, continue to work with some of the QB guru types on his arm, and have a Crompton-esque senior season, it's entirely possible that someone could choose to give him a shot in the late rounds.