Zenner gained 13 yards on three carries in Saturday's preseason game against the Ravens.
With Stevan Ridley released earlier in the week, Zenner is all but assured of a spot on the final roster. The two players were competing for Detroit's power-back job, which could be similar to the role Joique Bell filled last season. It's still unclear how much of a threat Zenner poses to the workload of lead back Ameer Abdullah.