One thing that I don't believe has been addressed before is the type of running back Riley has recruited. To me, they all run a different way then our current backs. I noticed it with the first two Rbs that committed.
The reason why I believe this is important is that it appears that those the kind of backs Riley likes, and that will affect their chances to getting playing time. As Stevenson is far and away the best of these new backs, he very well could be the #2 back after a couple games.
I also think Cross will be used more then others may think because he is a team player that does all the coaches ask of him. When your starting to coach a new team, you want to reward those players by giving them a chance.
Long story short, while a bunch of backs may be more talented, in my opinion, then others, it's the ones that fit in his system that have an advantage. (And yes, I know he says he adjusts his system to the talent around. But if some of the talent plays into his preferred system, then they have an advantage).