The San Francisco 49ers trail the St. Louis Rams 14-7 at halftime, and starting quarterback Alex Smith will not return to the game after suffering a concussion.

The 49ers, who were down 14-0 going into the second quarter, were able to get on the board after a 12 play, 78 yard drive that took up over eight minutes of playing time. Michael Crabtree completed the possession with a 14 yard touchdown catch from Smith.

But on San Francisco's next drive, Colin Kaepernick replaced Smith, who was injured on a helmet-to-helmet collision.

Alex Smith is out for the remainder of the game with a concussion.

— San Francisco 49ers (@49ers) November 11, 2012

Smith was 7/8 for 72 yards and a touchdown at the time of his exit. Kaepernick is 1/4 for three yards as his replacement.

Frank Gore, meanwhile, leads the 49ers with 51 yards on 11 carries. Crabtree is the team's top receiver with 59 yards and a touchdown grab.