Two cents, devalued for inflation: Analogous, I think, ancient history---The Detroit Lions were once a dangerous football team [yeh, I know it seems unlikely]. At the time they instituted a radical offensive scheme nick-named the "Silver Stretch". This offense spread the field both horizontally and vertically [sound a bit familiar??] with four wides and one RB [Barry Sanders]. The offense was the most terrorizing "fast strike" offense in the NFL until it got to about the five yard line. Usually it didn't have to worry about that, as either receivers or Sanders were scoring from 20 to 60 yards out.
The relevance to the current discussion I believe is this: although somewhat differently conceived, the Kelly spread does many of the same things, and his running back needs to have the analogous skills. OK, nobody else is Barry Sanders, but bear with me. In that offense very few "traditional" running plays were called for Sanders. [Later when the offense began to stink, it was different with fullback & block-oriented tight end]. The running plays called were largely "draw-like" plays, meant to scare the defense into greater slowness against this pass-first offense. Well, what the h--- does this have to do with us??
Sanders great years were when he was in the Silver Stretch, and could "create" with the football. The stretch gave him room. Kelly wants to create the same kind of "secondary-but-dangerous" threat with his "stretch". Kelly is, need it be said?, pass-first. Sanders value in the "surprise" run, was his shiftiness [of which there was none better], NOT his ability to run people over.
I believe, due to this "brilliant analysis" dimmed only by lack of knowledge and creeping senility, that what we need in a primary back in the Kelly Stretch, is a shifty back capable of locating emerging holes in a loose ruck, and making the first guy or two miss. Hayes seems to be that kind of runner. I suppose that Huggins is too. It's not as necessary that they plough people over. It's also nice if, once they DO make the first two miss, they can accelerate, as sometimes, like Sanders, they might take it to the house.
I saw Armando began to figure this out after a game or two. I thought that Cierre was going to be the guy, but he has trouble with seeing the hole. [and the line has trouble getting one for him; lineplay for this type of running isn't dead simple and takes time---similar to what you saw at WVA in Rodriguez' first couple of years]. i'm not sure that we currently have any ideal back for the stretch/surprise type running. I'll honor Armando till the end of days for what he gave the team this year, but Kelly needs a slightly different back. Hayes?? Huggins??
By the way, the Lions screwed up due to complaints about goal-line offense, and ruined their scheme. [Creating huge numbers of zero-yardage-running sideways in the backfield plays by their Hall-of-Fame RB]. ND wouldn't have to worry about that, as with our larger number rosters, we can easily create "Jumbo Packages" for goal-line violence.