Most underrated in this class and earliest impact are different questions, so I will throw my 2 cents in. The most obvious answer is Nuernberger since he will presumably start at kicker. But I will go ahead and make my bold predictions:
Offense: I like Samuel for skilled positions. Alot to like about Dixon but I think Samuel is a receiving threat that can run, whereas Dontre is a running threat that can catch. I say this because Samuel is a guy that can flat out make big plays happen if you get the ball in his hands. We need more of that on offense and I just think he is ready to go...I think you will see a legitimate 185-190 lb. Samuel by the time August hits and with no loss in playmaking ability. As for my bigs, I think we see Knox get in the early two-deep and push for a starting spot. He doesn't need much weight redistribution and is physically a grueling specimen. Lots of lower body strength and his talent is off the charts. I would not be surprised to see Meech take over a guard spot if anyone falters in any way.
Defense: I think we see 3 guys get some serious time on defense. McMillan seems like an obvious choice but I think Mitchell steps up and runs away with one of the spots (and one of Perry or Trey Johnson takes the other one/two spots). I see McMillan playing some regardless but he really needs to stay lean coming into Columbus...I could see him getting too big if he isn't careful. Either way, he plays some decent minutes. Booker could also get immediate time and thrive, all depends on how he picks up the game mentally. My next pick is Solomon Thomas if he comes here. If not, nobody on the DL. In the back 4, my pick is Webb...outstanding coverage skills and he could be sent in to shut down a good receiver. Erick Smith is also a great tackler and has fantastic instincts in coverage...I think he will be great, just no sure if it is right away. Lattimore will be awesome in the secondary, but stands to make a more immediate impact on offense.