LAKE FOREST, Ill. -- Nathan Vasher wouldn't rule out playing Sunday, but a noticeable limp and a cautious tone indicated the Chicago Bears may be without the cornerback when they visit the Detroit Lions.

The Bears' other starting cornerback, Charles Tillman, could also miss the game.

Vasher tweaked his groin in last week's 34-10 loss to Dallas, while Tillman suffered a high ankle sprain. Without Pro Bowl defensive tackle Tommie Harris (sprained knee), Pro Bowl linebacker Lance Briggs (hamstring) and strong safety Adam Archuleta (broken hand) the Bears' vaunted defense barely resembles a monster.

"I'm trying to battle back and see if I can get out there this week," Vasher said Thursday.

Will he play against the Lions?

"I still haven't gotten the heads-up about it," Vasher said. "I'm just basically sore right now."

The Bears held Vasher, Tillman, Briggs, Harris and offensive linemen Ruben Brown (ankle) and Fred Miller (knee) out of practice for the second straight day on Thursday. Archuleta and running back Adrian Peterson (calf) participated on a limited basis again, while defensive end Adewale Ogunleye (hip) and defensive tackle Darwin Walker (knee) were upgraded to full participation. So there was some good news for a team that's reeling.

"I expect to have everybody," coach Lovie Smith said. "I'm optimistic. My glass is half full -- always."

But reality has been quite harsh.

Besides the lengthy injury list, the Bears (1-2) are dealing with a change at quarterback after Rex Grossman threw three interceptions against the Cowboys. That finally convinced Smith to go with Brian Griese.

While Grossman dropped out of favor, other Bears fell like bad stocks against Dallas.

Briggs appeared to hurt himself in the second quarter trying to avoid Brian Urlacher, who sacked Tony Romo. He stayed in the game, but did not come out for the second half, and the injuries piled on from there.

Vasher, a Pro Bowl pick in 2005, and Harris left the game in the second half. Archuleta stayed in after breaking his wrist in the third quarter. And Tillman was seen kneeling on the same play Vasher hurt himself, although he said this week he's fine.

Archuleta, who has been wearing a soft cast on his right hand, hopes to play this week.

"We're going to see what happens," he said. "It's not like a set protocol. We're just going to see how it goes throughout the week."

Vasher sounded like a man who was hoping for the best, not expecting it.

"It felt bad," he said. "I kind of planted the wrong way and my foot got stuck in the ground. I've made that transition, cut, 100 times but you never know what's going to happen during the course of the game."

If Vasher and Tillman can't play, the Bears likely would go with Ricky Manning Jr. and rookie Trumaine McBride.

Manning and McBride would face a tall order against the Lions, who boast the league's most prolific passing game and a tall set of receivers. Detroit is averaging 345.3 yards per game passing. And the 6-foot-2 Roy Williams is third in the league with 335 yards receiving.

The Bears' secondary had already taken a huge hit before the latest round of injuries when former Pro Bowl safety Mike Brown -- one of the emotional leaders of the defense -- ruptured the anterior cruciate ligament in his left knee in the opener. Moments later, the defense suffered another blow when starting nose tackle Dusty Dvoracek went down with a similar injury.

Walker replaced Dvoracek, and now, he might fill in for Harris. If that happens, Anthony Adams could take Walker's spot on Sunday.

If there's any consolation for the Bears, it's that the Lions allowed nine sacks in last week's 56-21 loss to the Philadelphia.

"They're a good football team," defensive coordinator Bob Babich said. "Hopefully, we get a lot of pressure on them. The way we're looking at it, we've got to go out and do it."

Babich feels "really good about our defensive line." But the secondary?

"Our pass coverage after last week, we need to improve it," he said. "We felt like some fundamentals and things like that ... we're working hard this week to get that stuff cleaned up. The first two games, we were very comfortable with it."

Copyright 2007 by The Associated Press