Jay Cutler took another positive step in his recovery from a concussion he sustained Nov. 11 against the Texans, practicing Friday on a limited basis for the second straight day.
The Bears quarterback, who sat out Monday's loss in San Francisco, was listed as questionable for Sunday's home game against the Vikings. Cutler must be cleared by an independent neurologist he's scheduled to meet with Saturday in order to play Sunday.
In the past two seasons the Bears are 14-5 when Cutler starts and 1-6 when he doesn't. The offense has scored 41 touchdowns in his 19 starts and only seven TDs in the seven games he's missed.
In other injury news, tight end Kellen Davis (ankle) was limited in practice Friday and listed as questionable. Defensive end Shea McClellin, who already has been cleared to play after missing the 49ers game with a concussion he suffered against the Texans, is probable.
For the Vikings, receiver Percy Harvin (ankle) did not practice and is doubtful; while defensive tackle Letroy Guion (foot) and guard Charlie Johnson (toe) both were limited and are questionable.
Tough test: The Bears defense will be challenged Sunday by Vikings running back Adrian Peterson, who leads the NFL in rushing with 1,128 yards and seven touchdowns on 195 carries.
Peterson averaged 122 yards in his first six games against the Bears, highlighted by a 224-yard effort in a 2007 contest in Chicago. But he's been held to 51 and 39 yards in the last two meetings.
"We've seen him at his best at Soldier Field," Smith said. "Right now it just seems like he's playing at his best. He's one of the best players in the league. It's been like that for a long time. We know him, he knows us. It'll be a big challenge for us."
Peterson's performance this season is even more remarkable when you consider that he underwent surgery after tearing the ACL and MCL in his left knee last Dec. 24.
"It's saying a lot," Smith said. "You have a major knee reconstruction, and you would have to know that he went through that because that's not what you see on video right now. It looks like he's 100 percent and he hasn't missed a beat."
Bouncing back: Dominant throughout a majority of the season, the Bears defense is determined to rebound from its worst game of the year Monday night in San Francisco.
Making his first NFL start, quarterback Colin Kaepernick led the 49ers to two touchdowns and two field goals on their first four possessions en route to a 32-7 victory.
"Nobody takes that well," said defensive coordinator Rod Marinelli. "They have pride; that's why you know that if a bunch of men are going to bounce back, it's these guys. They have tremendous pride and we'll bounce back. That's what we do."
"We have a history together," Smith added. "Through the course of a year there are a lot of good football teams that sometimes you think you're going to play a certain way and you don't. You have some games where you say, 'Where did that come from?' But we know how to bounce back. I've seen them do it. We're a good football team. We'll bounce back this week."
Where's Waldo: The Bears offensive line also will face a difficult task against defensive end Jared Allen, who leads the Vikings with seven sacks.
"Definitely we will have chip help," said offensive coordinator Mike Tice. "He knows that. We're going to have to make sure we account for him every play. Every time we drop back to throw the ball, he's 'Waldo.' We have to make sure we know where he is and find him and make sure we have an answer for that, without a doubt."
In last year's regular season finale against the Bears, Allen recorded 3.5 sacks to increase his season total to 22, half a sack behind Michael Strahan's single-season NFL record set in 2001.