If the 49ers are going to make a run at the NFC West title, they'll have to do it without the centerpiece of their offense.
Gore had runs of 25 and 15 yards on San Francisco's opening possession, but went out later in the drive. He returned for two plays to start the next drive, but spent the rest of the first half on the sideline without his helmet.
The 49ers announced in the third quarter that Gore wouldn't return for the second half. He had 52 yards on five carries before getting hurt. Veteran Brian Westbrook received his first extended playing time of the season in Gore's absence, rushing for 136 yards and a touchdown.
Gore's injury comes at a terrible time for the Niners, who have won four of their last six games to pull within one game of the St. Louis Rams in the NFC West.
With quarterback unrest serving as a running subplot in San Francisco's season, Gore has been the unquestioned focus of the offensive attack. In 11 games, the Miami product had 1,305 total yards and five touchdowns, numbers that will in all likelihood represent his final totals of the 2010 season.