ALLEN PARK, Mich. -

Theo Riddick signed a three-year contract extension just before the start of the season. Now, the Detroit Lions are about to make him earn it.

The Lions placed starting running back Ameer Abdullah on injured reserve Wednesday after he underwent surgery to repair his left foot.

Abdullah will miss a minimum of eight weeks and could miss the rest of the season, and the Lions will use a combination of Riddick, rookie Dwayne Washington and others to prop up their surprisingly effective backfield in his absence.

"Obviously, Theo is the veteran guy back there, the most productive guy that we've got back there at this particular point in time," Lions coach Jim Caldwell said. "He's the lead guy. But the fact of the matter is, there'll be some other guys carrying the ball as well. It just depends on how much, depending upon exactly what type of attack we decide to use."

Riddick established himself as one of the best pass-catching running backs in the NFL last year, when he caught 80 passes but was used sparingly in the run game.

The Lions talked openly about expanding Riddick's role as a rusher this fall, but did that only modestly through the first two games of the season.

Riddick ran for 45 yards on seven carries in the Lions' season-opening win over the Indianapolis Colts, and had a career-high 11 carries -- eight of them after Abdullah's injury -- in last week's loss to the Tennessee Titans.

Caldwell said Riddick is "more than capable" of shouldering a bigger load on offense. The Lions enter this week's game against the Green Bay Packers with the league's ninth-ranked rushing attack at 126.5 yards per game.

"Guys got to step up and play," Caldwell said. "Somebody's got to take a few more carries then they would have ordinarily, and obviously I think we have a number of guys that can do that for us."

Washington, a rookie seventh-round pick out of the University of Washington, also is in line for an expanded role.

The Lions' goal-line back in Week 1, Washington ran for 31 yards on four carries against the Titans. He opened eyes with a strong preseason, when he returned a kick 96 yards for a touchdown and scored on a 58-yard run, and is a more natural runner than Riddick.

Zach Zenner, who was inactive in Weeks 1 and 2, also will see time as the Lions' No. 3 back.

"We have guys that can play, I think, have been productive and have proven to be productive," Caldwell said. "It's just a matter of how many times they touch it. We feel good about the guys that we have in that spot."