Starting left tackle Joe Staley went into the team's locker room with a right knee injury he suffered on the opening drive and has been ruled out for the rest of the game. With starting left guard Mike Iupati already out with his own knee injury, the 49ers have had to reshuffle their offensive line for the first time in three seasons.
Right guard Alex Boone has moved to Staley's left-tackle spot where he will battle the Rams' Robert Quinn, who is second in the league in sacks and who is a candidate for Defensive Player of the Year. Joe Looney, who made his NFL debut Monday against the Redskins, is in at right guard while Adam Snyder is lined up at left guard.
Staley suffered an injury scare when the teams met in St. Louis earlier this year but the injury did not turn out to be serious. His last major injury -- a broken leg -- also came against the Rams, an overtime win in 2010. He returned to that game after being injured in the fourth quarter. He sat out the rest of that season.
Staley tested the knee on the 49ers sideline in front of doctors, at one point hopping on one leg. After that, he walked slowly into the locker room while favoring his right leg.
-- Matt Barrows