Chicago Bears quarterback Jay Cutler and Philadelphia Eagles passer Michael Vick will both miss their teams' games this week due to concussions.

The Bears said Friday that Cutler will sit out Monday's game at San Francisco, with backup Jason Campbell expected to start in his place.

"You definitely don't want to see anyone get hurt or injured in this business," said Campbell, who's made 70 starts in his career with Washington and Oakland. "We understand it is a tough sport. Sometimes, things like that happen."

Cutler's status was in question after he sat out the second half of Sunday's loss to Houston. The Bears believe he was injured on a helmet-to-helmet hit by the Texans' Tim Dobbins, who was fined $30,000 US by the league, late in the second quarter.

Star receiver Brandon Marshall said Cutler is getting better, but he also said there's a bigger picture that goes beyond this week's game.

"Our life, our health, is more important than football," Marshall said. "I think we'll get Jay back sooner than later."

Cutler initially did not show any symptoms and took seven more snaps in the first half. It wasn't until halftime that the symptoms showed up, and the Bears went with Campbell in the loss to Houston.

The concussion isn't the first for Cutler. He missed a game after being sacked nine times in the first half of a loss at the New York Giants in October 2010. Last year, Cutler broke his right thumb late in a win over San Diego that put Chicago at 7-3. His replacement, Caleb Hanie, struggled and the Bears lost five of their last six.

Campbell part of retooled roster

That cost general manager Jerry Angelo his job. Phil Emery replaced him and retooled the roster, landing Marshall in a blockbuster trade with Miami and addressing several other areas, including backup quarterback by signing Campbell to a one-year deal.

The 49ers, meanwhile, could be without starting quarterback Alex Smith, who suffered a concussion of his own last week. He practiced in a non-contact black jersey Wednesday and Thursday and hopes to be ready to play against Chicago.

Vick will miss the Eagles' game at Washington on Sunday.

Rookie Nick Foles, who replaced Vick during the 38-23 loss to Dallas on Sunday, and who practiced with the first team all week, will get his first NFL start in a battle of 3-6 teams fighting to save their seasons.

Philadelphia coach Andy Reid made the announcement Friday at the team's practice facility, confirming a decision that had been in the works since Monday. It was only because Vick had not completed the league-mandated concussion testing earlier in the week, that Reid did not officially rule him out until the team's final practice.

2 concussions 'different'

Head trainer Rick Burkholder spoke to the media on the field after the announcement.

"With concussions, they're all different," Burkholder said. "We needed to take it day by day. His two concussions he's had with us have been different."

Vick, who completed just six passes for 70 yards against Dallas, did not practice all week.

"He has too many symptoms for us to even exercise him," Burkholder said. "He's not even close to playing this week."

Foles was 22 of 32 for 219 yards with a touchdown and an interception vs. the Cowboys. Those numbers weren't enough to help the Eagles avoid their fifth straight loss, a first in Reid's 14 seasons.

Vick has been inconsistent, at best, the last two seasons. After helping to rally the Eagles from a 4-8 start last season with four consecutive victories to close the year, he has thrown for 11 touchdowns with nine interceptions this season, and compiled a rating of just 79.2.

As for this weekend, Burkholder said Vick simply needs rest, and the process now will include getting him "in dark, quiet places."