I'm no longer in favor of redshirting freshmen running backs. Just too many injuries at the position, in addition to all the other reasons that players leave (academics, homesick, family problems, legal issues, disputes with coaching staff, etc) that Iowa seems to have a lot of.
If Coker can get healthy enough to practice the week of the EIU game, play him in that game (if only a few snaps). I believe they will play DeAndre Johnson (given Hampton suspension and Wegher not around).
If a freshmen back can be healthy and productive enough to help in even one game, I say play them. In the Ferentz era, the percentage of scholarship running backs who play at Iowa as a 5th year senior is low (not counting former walk-ons like Paki).