He finished with seven carries for a team-high 24 yards, which doesn't sound like much, and even he says he has a lot to work on.
Breaking a 20-yarder in the fourth quarter, against guys who are going to be selling cars in a month, is not the same as grinding out a 12-yarder against the Steelers' starting defense (minus a couple regulars).
Ameer Abdullah is still working his way back from a shoulder injury, so Zenner was used as Detroit's No. 1 rusher in this game. Theo Riddick started and had four carries, but as the story pointed out, perhaps most revealing is Stevan Ridley had no carries until the second half. With Riddick more of a pass-catcher, the competition for backup to Abdullah seems to be between Zenner and Ridley.