He didn't practice Friday because of his sore left ankle and was ruled out after practice, as was first reported by ESPN.com's John Clayton.
The former NFL MVP, who was hurt in Monday night's 24-20 win at Oakland, hadn't missed a game due to injury until January, when a groin injury kept him out of a playoff loss to the eventual Super Bowl champion Pittsburgh Steelers.
Also out are center Nick Hardwick (ankle) and defensive end Travis Johnson (groin). Right guard Louis Vasquez (knee) could also be sidelined, along with linebacker Antwan Applewhite (hamstring) and defensive tackle Jamal Williams (elbow). All three are listed as questionable for Sunday.
The Chargers have the wrong opponent to not be at full strength. They expect a tough, physical game against the hard-nosed Ravens, who advanced to last season's AFC Championship Game before losing to the Steelers.
The previous year it was the Chargers getting one win away from the Super Bowl before losing to the New England Patriots.
"You've got two teams that are awfully good and see themselves as being pretty good," coach Norv Turner said Friday. "They are a very physical football team and we are a physical football team. So I think it's going to be a heck of a matchup. We both have aspirations of doing something very special. Both teams would like to have the kind of year to get there again."
Both squads are coming off wins over AFC West opponents. The Chargers beat Oakland 24-20 and the Ravens beat the visiting Kansas City Chiefs 38-24.
"I think playing in our home stadium is big for us," Turner said.
Senior NFL writer John Clayton and The Associated Press contributed to this story.