Lions RB Theo Riddick placed on IR with injured wrist

ALLEN PARK, Mich. -- The Detroit Lions will be without their top two running backs for the rest of the season.

The Lions placed Theo Riddick on injured reserve Saturday with a wrist injury. He joins Ameer Abdullah, the team's initial starting running back, on IR after Abdullah suffered a foot injury in Week 2 against Tennessee.

The Lions have given no specifics about Riddick's injury other than Jim Caldwell saying earlier this month that "he's healing." Riddick has not practiced the past two weeks, although he was spotted at practice each day in a baseball cap.

With Riddick out, the Lions will once again lean heavily on Zach Zenner as the team's primary running back in Sunday night's NFC North title game against the Green Bay Packers. Zenner got a surprise start in Week 16 against Dallas and had a career-high 67 rushing yards. He could be spelled by either rookie Dwayne Washington or veteran Joique Bell, who has yet to have a carry for the Lions this season.

This means Riddick finishes his fourth NFL regular season with 357 rushing yards -- still a team best -- and 53 catches for 371 yards receiving.

Detroit signed slot receiver Jace Billingsley from the team's practice squad to take Riddick's spot on the roster.

The Lions are also likely to be without their starting center, Travis Swanson, for the fourth straight game as he recovers from a concussion. Swanson practiced on a limited basis all week but was listed as doubtful against the Packers.

The biggest question leading into Sunday night will be cornerback Darius Slay. The Lions' top cornerback and the player who would most likely defend Green Bay receiver Jordy Nelson, Slay is officially questionable. He's practiced all week on a limited basis but declined to speak with the media Wednesday, Thursday and Friday.

Linebacker DeAndre Levy was listed as questionable again with an injured knee but has been playing with the injury the last few weeks. Returner/receiver Andre Roberts was listed as questionable with a shoulder injury. He didn't practice Wednesday or Thursday and had a red no-contact jersey on Friday.

The Lions also added starting RT Riley Reiff to the injury report Saturday as questionable with a hip injury.