Bears S Anthony Walters may get his first-career start with Chris Conte likely out. (US Presswire)

If LB Brian Urlacher is to make a comeback from a hamstring injury, it will be on just two  days of practice. Urlacher, who hasn't practiced since a hamstring injury in the Dec. 2 loss to Seattle, missed a light Bears' practice Wednesday along with a number of key players who had injuries of varying severity.

Besides Urlacher, CB Charles Tillman (ribs-elbow), RB Matt Forte (ankle), LB Blake Costanzo (calf), S Chris Conte (hamstring), and RB Armando Allen (knee) did not participate. 

Tillman's injury is not serious, but Forte remains a question. And with Allen out, the Bears are down to a player who wasn't even on the team two weeks ago -- Kahlil Bell -- taking all the practice snaps.

"His ankle is looking pretty good," coach Lovie Smith said of Forte. "And of course it’s a big football game and then they’re all big and we always play guys when they’re healthy and ready to go and hopefully that’s the case with Matt. He’s pretty encouraged by what’s happening."

Forte missed practices before playing following a knee sprain twice before this year. 

The running back situation didn't seem to worry Smith.

"We’ve had to shuffle a little bit the last few weeks just in general, but that’s not the normal amount that we would have, so it’ll be a little bit of an extra load for some of the guys early in the week. But hopefully, by game time we’ll have the full allotment of our running back ready to go."

Safety first: The free safety issue might be the biggest facing the Bears because of Calvin Johnson being a deep threat. Conte would appear to be unlikely to play and Anthony Walters, who has never started a game, may have to replace him.

"He’ll be out a while," Smith said. A while could mean the rest of the season if the Bears fail to make the playoffs or play a single playoff game.

The Bears have held opposing QBs to a 69.8 passer rating this year with Conte and Major Wright starting every game. In their 21 starts together, opposing QBs have a 68.9 passer rating. 

The last time the Bears played Detroit without Conte starting was at Ford Field, Oct. 10, 2011. Matt Stafford found Johnson for a 73-yard TD pass and Megatron had five catches for 130 yards, and the Lions also had an 88-yard TD run by Jahvid Best. With all the big plays, the Bears obviously had no one home in the middle deep. Chris Harris was playing safety then for the Bears.

Walters said he'll rely on his Pro Bowl-studded lineup for assistance.

"I think those guys can help take some of that pressure away," he said. "All I have to do is be where I'm supposed to be when I'm supposed to be there. And those guys make plays. We scored two defensive touchdowns last week."

Relief help: With only two healthy safeties, the team added former Texans and Dolphins S Troy Nolan. The 6-foot-2, 200-pounder was a seventh-round pick by the Texans in 2009. He has 73 tackles, three INTs. 

He's anticipating nothing more than special teams play this week, if that. The Bears say they have other options at safety. That would mean converting a corner to safety, but they're not saying which one would move.

“It’s very hard to learn a playbook in this amount of time, but I’ve just got to pick up what I can pick up and just go with it like that," Nolan said. "I’ve just got to stay ready and just get in with the coaches.”

Better injury news: DT Henry Melton practiced on a limited basis, as did T Jonathan Scott. Both missed last week's game. Melton's addition could be huge for the pass rush.

"(Against) a team like thism it would be important to get a dominant inside player that can rush the passer and play the run, too," Smith said. "Henry knows what’s at stake, too, and hopefully we’ll have him."

Follow Bears reporter Gene Chamberlain on Twitter @CBSBears.