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Theo Riddick scored two touchdowns last week against Philadelphia, but won't play this week against Los Angeles.

(Mike Mulholland | MLive.com)

ALLEN PARK -- The Detroit Lions said they weren't overly concerned about the loss of Ameer Abdullah because they still had Theo Riddick.

But now they've lost him too.

Riddick did not practice all week because of an ankle injury, and has already been ruled out by the team for Sunday's game against the Los Angeles Rams. Linebacker DeAndre Levy, tight end Eric Ebron and defensive tackle Haloti Ngata also won't play.

Defensive end Ezekiel Ansah has been upgraded to questionable, after missing the last three weeks with a high ankle sprain. He should play.

Receiver Anquan Boldin, defensive tackle A'Shawn Robinson, running back Dwayne Washington, safety Don Carey and guards Larry Warford and Laken Tomlinson are also listed as questionable.

Of all the names on Detroit's lengthy injury report, Riddick's is the most concerning. He moved into a starting role after the loss of Abdullah, who is on injured reserve recovering from foot surgery.

Riddick also is an important part of the passing game, where he led the NFL's running backs in catches last year. He has 26 more this year, which is just one off Marvin Jones' team lead. His three receiving touchdowns match a team lead, and he scored two of them in the win against Philadelphia last week.

But Riddick apparently suffered an ankle injury sometime in that game, and now it becomes unclear who Detroit will turn to in the backfield.

The only healthy guys back there are Zach Zenner, who began the season as a healthy scratch and has 10 carries for just 21 yards, and Justin Forsett, who was signed this week.

Coach Jim Caldwell indicated Forsett, a 10th-year veteran, could be ready to contribute this week.

"It doesn't take long," Caldwell said. "You can sense that guy knows how to learn, how to examine things, how to relate one system to another and be functional in a hurry. So we'll see what happens."

Is Zenner ready for a bigger role?

"Sure, yeah," Caldwell said. "No question he's certainly capable. He's productive, yeah there's no question about that."

Washington had been a productive back for Detroit the first weeks of the season, but he went down with an ankle injury against Chicago and missed last week's game against Philly. He practiced just once this week, on Friday, and is listed as questionable for the game.

Detroit could also get creative in replacing Riddick. Coordinator Jim Bob Cooter lined up receiver Golden Tate in the backfield last week, and that could be a look they go back to, especially if they are in need of pass-catchers out of the backfield, which is Riddick's speciality.

"He's got uniqueness, which is obvious," Caldwell said. "You just don't find many guys, if you check through history, that do what he does. But we do have, if he cannot go, for whatever reason, we do have a number of guys that I think are capable of doing the things that we need to get done.

"We may not do exactly the same things we do with him. But in terms of our offensive scheme, it doesn't shut down a whole area in our offense. We just maybe have to do it a little different way."