IMO, 80% of the evaluation of a RB can be made by watching him for 15 carries and then answering the question "can he make the first guy miss?"
Using that criteria, non of our guys escape the "serviceable" category but that's ok. They will be improved and would be good enough to be a functional part of "a good running system". The primary problem isn't RBs or OL, it's lack of "a good running system". (scheme)
Last year we were 12th in the B10 in avg yards gained on 3rd and 3 or less.
That's actually better than some other recent years when we were probably 3rd worst in the country instead of just the conference. Why? Lack of misdirection, zone blocking giving away point of attack, formation so tight that there are no RB options (even Gayle Sayers needed SOME gap).
So maybe we do better in longer yardage situations? Well, only if we consider finishing 11th in the conference as doing better, That's where we finished last year in avg yards gained on 1st down running plays.
This offense has some serious systemic deficiencies and a discussion about coaching improvement would be more relevant.