ESPN.com’s Adam Schefter reports that the injury is “bigger than people realize.”
Rivers did not practice Wednesday and is listed on the team’s injury report as having chest and back injuries.
“I hate not practicing but at some point you've got to do what's best for me and the team. Practicing today just wouldn't have been beneficial moving toward Saturday,” Rivers said, according to the Associated Press.
Chargers coach Mike McCoy also said he expects the five-time Pro Bowler to play against San Francisco.
Rivers was asked if he plans on practicing Thursday.
“We'll see. I don't think there'll be any fireworks," he said.
The Chargers are battling for a playoff spot but have lost two in a row and need help from other teams. Rivers has completed 68 percent of his passes for 3,639 yards with 27 touchdowns and 13 interceptions this season.
- Scooby Axson