Zenner's teammate Dwayne Washington (quadriceps) is expected to miss multiple games, the Detroit Free Press reports.
Zenner will fill in as the No. 3 back, starting with Sunday's game against the Falcons. The role figures to include a portion of the early-down carries and goal-line work, but the Lions have a strong preference for their passing game even when they're close to the opponent's end zone. Zenner won't be of much interest unless Ameer Abdullah also suffers an injury.