Great question of course. The class has stars at every position, but no indisputable "can't keep him off the field" guys. So the analysis is really what position has unproven or questionable depth.
QB is set for 2015. OL is looking decent, and is tough to make an impact for a freshman, even a great one. The secondary is a strength.
The rest of the positions have opportunities in the two deep. WR seems to be one of the easier positions for a freshman to impact. Philpott? We aren't deep at ABack, and we typically like a deep rotation there. I expect one, maybe two to break into the lineup. IIRC, we are two deep at BBack. If we stay healthy, we might redshirt everybody there.
DL depends a lot on Days' grades. DL is a bad spot to have to put an 18 y/o, but we might have to play someone.
Last is LB. The players we have will be a year stronger and smarter. I don't think we rotate LB excessively, so I think we will be careful about burning a redshirt here, is my humble opinion.
tl;dr. WR, probably Philpott and Stewart, but Howell has the leg up. AB, total guess, best two, Mitchell and Cottrell? And a DL, probably Anree, but Kyle has the leg up here. iMHO, any more will be due to injuries or unforeseen losses.