I'm surprised nobody has mentioned how KF tends to ride his horse until it can't run anymore. In 2010 we never saw Coker or Rogers once the B1G season was under way. No Coker until ARob had his bell rung.
So we see a single, dependable, all purpose back with lots of yards then the next guy has 1/10th the yardage. Typical 90/10 distribution. I think total yardage goes up if the distribution goes more like 70/30 or a 60/40 split, probably in the +15 percent range. Add a third so we have a 50 / 30 / 20 split or something similar and we may get an additional +5 percent or so. The natural distribution starts to work against you when add a fourth or more elements taking more away from the top performers tha566n you gain.
This is why Iowa is middle of the pack. You are trading +20% total team yardage for +15% for a single individual. The teams that are ahead of Iowa in total yards will have something like two running backs and a QB sharing carries. Iowa's top back may have more individual yards than these team's top running back. There are few, if any, other rushing yards for Iowa. In fact, there essentially wouldn't be any other rushing yards if it wasn't for injuries to the primary Iowa ball carrier.
The reason is that individual runners will have certain strengths that can be exploited against certain weaknesses of opposing teams. For example if the opponent isn't good covering the outside run, Iowa will run stretch plays against them. The all purpose Iowa running back is going to get three digit yardage because the line is making it happen. If Iowa has an outside specialist so to speak, a guy that can turn the corner a little sooner than the all purpose back then he might have even more yards running the exact, same, plays.
Against another team that has LBs who are not great tacklers a runner who is slippery is going to gouge them for a couple more yards per carry between the tackles.
You can run combos like a powerhouse straight ahead runner earlier in the game and as the defense tires swith to the outside guy down the stretch.
This is with the same plays called, just w/ different players on the field.
We have what looks to be four RBs and at least one QB that should be able to run behind what is shaping up to be a typical Iowa line. I hope we don't go throgh them in serial fashion.