Personally i think this is the staff's attempt to get a 3rd down back. Since D-Tray left, we are lacking a big back, so I think this is them attempting to work with what they got. Honestly I would be very surprised if I saw Okafor turn anything here, but with Brown coaching I guess can never tell. That dude's got some coaching skills.
The whole "big back" concept is kind of trite I think, especially within our system (or what I think our system will be). Rex Burkhead is a perfectly capable 3rd down back. Even when we had D-Tray last year, we never used him (and I don't think that's where the offense went wrong). Furthermore, it appeared that he transferred because he was a "big back," and we were clearly not going to have any real use for him in our offense.
I think the coaching staff wants guys who are every-down backs, like Roy Helu and Rex Burkhead were. I think they're working Okafor not because we need a "big back" or a "3rd down back," but because without the three freshmen coming in, we are very shallow at RB, and we desperately need someone with some athleticism like Okafor to step up.