The only one I've seen is RVZ, if he's healthy, he's got the best ball skills I've seen in a game from an Iowa WR since McNutt maybe? Just spatial awareness and the ability to go up and get it. We need to see Diaz do it, but when you've got Lester, Barnes, and Kirk with their public comments about him, plus the fact Bama offered him, hard for me to believe he isn't the real deal, when was the last time Kirk was publicly praising a WR like that?
Behind those two there seems to be some depth/upside between Howard/KJ Parker/James, though I'd agree less proven and likely more on par with what they've had historically until we see otherwise.
The only real concerns I have on this team talent wise is DT & QB, I think they'll be pretty good everywhere else, definitely younger than I'd like to see, but the talent is there. Unfortunately, those two positions might be the two most important to unlocking the ceiling of this team.
EDIT: And as long as you get one of the two (i.e. DT or QB overperforms), they probably still have a pretty high ceiling, you can survive QB being below average if DT play excels, or you can survive suboptimal play at DT if QB excels. If you miss at both DT and QB, that's the formula for 7-5 or 8-4, especially if you mix in a couple of injuries at other positions.