I'll add my two cents. JJ McCarthy right now is a fringe NFL starter. But...there is a huge but. I'm guilty of this as well and I've only started to think about this in another way.
GMs and teams won't be looking at him McCarthy for what he is right now. They are looking at what he could become. His tape is lackluster and frustrating. Michigan didn't ask him to do too much. So my point is we don't know what he is truly.
McCarthy is extremely young at the QB position. He made a lot of dumb mistakes because he needs more reps. However, from his first year to his junior year -- dude made pretty big strides. He played in a pro offense and made NFL type reads. He constantly played against some of the toughest defenses in all of college the last 2 years.
The efficiency numbers are there. Teams that are very analytically driven will love this kid. McCarthy this past season was extremely effective when it 3rd downs, throwing on the move, throwing when pressured or blitzed, and in the 4th quarter.
The mobility to move up and around the pocket is pretty big. I think he's going to light up the Combine and should run around a 4.5 or 4.6. Doesn't seem like much but if a 4.8 Patrick Mahomes could gash a defense running then McCarthy is deadly on the run. He isn't Lamar Jackson but running is a huge part of his game.
Lastly, the arm talent is there. It just isn't consistent. His mechanics aren't extremely clean. He has a little bit of a long wind up. However, he has the arm to make pretty much every throw. He is better throwing darts then throwing touch passes. He needs to work on his deep passes.
So after all of that, I would be very weary if you're projecting him past the 1st round and past the top half of the first round. I think teams see a QB that is efficient, is mobile, and having a pretty big arm. I would think a team like the Vikings would be all over this kid.