CHARLOTTE, N.C. - Panthers running back DeAngelo Williams is "doubtful" for this weekend's game against the Chicago Bears, the latest setback for Carolina's ground game.

Williams, who had just returned to the Panthers' lineup after missing the last two games with a bad hamstring, suffered an ankle injury during the second quarter of Sunday's game against the Baltimore Ravens.

"His foot's sore," Panthers coach Ron Rivera said Monday. "It doesn't look like it's anything structural, but it's sore. So he's probably going to start this week off as 'doubtful.'"

Williams, who was seen in the locker room Monday wearing a walking boot on his left foot, will be reevaluated later this week, the coach said. His absence from the lineup, however long it may be, further hits a Panthers roster already thin at running back.

Pro Bowl fullback Mike Tolbert was put on short-term injured reserve last week with a hairline fracture in his left leg, and will not be eligible to return to the lineup until mid-November. Jonathan Stewart (sprained right knee) and Fozzy Whittaker (quadriceps) are out indefinitely, and backup fullback Richie Brockel hurt his ankle Sunday.

That leaves Charlotte with only two healthy running backs — undrafted rookie Darrin Reaves, who had 26 yards on 12 carries against the Ravens, and free agent Tauren Poole, who fumbled on his first career carry last week.

"I'm sore, but I'm glad to be sore," said Reaves, who Rivera has said will be the starter in this weekend's game against the Bears. "I hadn't played that much in a long time, but I'm feeling good. I couldn't let myself feel overwhelmed by the situation. It was like, 'Okay, it's my time, so let's go.' I had to go do it, because my team needed me.

"It feels good. I'm starting to be able to live my dreams out, and that's a good feeling. Not under the circumstances we have, with so many guys dinged up, but it's still a good feeling."

The effect of the injuries on the Panthers' offence was evident against Baltimore. Carolina finished with 67 rushing yards, the third straight game the Panthers have failed to gain at least 100 yards on the ground.

Rivera said that Panthers officials are considering bringing in a free agent to shore up Carolina's running game. That's how both Reaves and Poole got to this position — first as additions to the practice squad, then called up to the 53-man roster after Stewart and Tolbert both went down.

"We're going to have to look at some guys from the outside right now, just to see," Rivera said. "Obviously, without Jonathan available last week and potentially not available this week, we've got to have an insurance policy just in case.

"There's some guys that are out there that we'll take a look at, try and see what their background is and see if they can handle it mentally. That's probably the biggest thing."

Rivera said that Whittaker would return to practice on Wednesday. However, his status for this weekend's game, like Stewart and Williams, is still undecided. Brockel said his injury wasn't structural, and that he should be ready to play against the Bears.

"We'll see how (Stewart) is on Wednesday," Rivera said. "He did a little bit of work on Friday and Saturday, and didn't look as good as I was hoping. We'll see how he is come Wednesday when he does some more work.

"Fozzy did some good things for us (in the preseason), but he's coming off an injury, so I don't know how available he'll be. That's why hopefully Reaves will continue to get better, and if we end up having an emergency guy come it, hopefully that's the kind of guy who can pick it up."