49ers QB Alex Smith out with concussion, Colin Kaepernick in

Forty-Niners quarterback Alex Smith took a big hit from Rams linebacker Jo-Lonn Dunbar midway through the first half but finished the drive with a touchdown pass to Michael Crabtree that made it 14-7, St. Louis. But after a Rams' three-and-out, Colin Kaepernick was under center for San Francisco and that's where he will remain the rest of the day.

Smith is done for the day after suffering a concussion. (US Presswire)

Forty-Niners quarterback Alex Smith took a big hit from Rams linebacker Jo-Lonn Dunbar midway through the first half but finished the drive with a touchdown pass to Michael Crabtree that cut St. Louis' lead to 14-7. But after a Rams' three-and-out, backup Colin Kaepernick was under center for San Francisco, and that's where he will remain the rest of the day. 

Smith has been ruled out with a concussion.

Smith was 7 of 8 for 72 yards and a TD pass before he went to the bench where he was checked out by the team medical staff. He eventually made his way to the locker room.

Kaepernick, meanwhile, was the team's second-round pick in the 2011 draft. He has been used mostly in wildcat situations this season but he'll get an expanded look at the playbook against the Rams.

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