It's not just Kelly's offense which is complex. Lou Holtz didn't start freshman RBs in his option attack. And let's be candid, the RB didn't have any decisions to make. It was the QB that made the read and the decision to hand off or not to the FB. Then it was the QB's decision again make the next read and pitch the ball or keep it. IF the QB pitched it, the RB had to catch the pitch and make one decision, go wide or cut inside. Rod Culver and other talented freshman like him STILL had to work themselves into the rotation by demonstrating capablity. Blocking was a skill Holtz expected his RBs to do. Most HS stud RBs do little of that in HS.
When Julius Jones was a freshman, he got used sparingly in the first 5 or 6 games and fans groaned loudly. He was a much better athlete than those playing ahead of him. After he finally got to start he was interviewed and asked about having to stand on the sidelines in those early games. He commented that he needed every bit of that time to learn the plays, the audibles, and the skills he hadn't HAD TO develop earlier. The speed of the game was faster but his legs could deal with that. It was his brain that had to work harder to process all the new material and be on the same page with his QB.
When Clausen was a freshman some fan was screaming for a new RB to start as the playbook wasn't so difficult. I replied, "It is pretty simple to memorize a few hundred pages. But the price for not being fully ready to play will be clear when the ref calls a time out and the cameras zoom in on the trainers working on a motionless form on the ground you'll hear in the background from that rookie RB, "Sorry man, I didn't realize that audible made be blitz protection. I though I was supposed to run a wheel route. Can you move your legs yet, Jimmy"
It's not just about which hole to hit.
Right now ND has two QBs, Rees and Hendrix. Looking at Tommy's limited mobility viz a viz the Lombard Whiff, and then the 4th quarter offense without Rees, ND can't afford a RB on the field that can't adjust to audibles seamlessly, can't read blitz, nor be able to provide pass protection when it's necessary. Otherwise we'll be down to one QB.
Bryant and Folstean are still asking directions to get around campus. Alford, Martin, and Kelly will have then on the field as they show they can handle all the aspects of the position.