Quarterback Alex Smith left the game at the end of the first half with a concussion and will not return. Smith took several big hits during an opening half in which the 49ers were outplayed -- and out-hit -- by the Rams, including a big shot from behind linebacker Jo-Lonn Dunbar.
That hit occurred at the end of the first quarter. Smith played another series in which he threw a touchdown pass to Michael Crabtree before being removed from the game.
Smith suffered a concussion in Week 2 last year but it was not diagnosed until after the game. He did not miss any playing time. Smith was 7-8 for 72 yards before leaving.
Second-year player Colin Kaepernick entered in Smith's place and promises to have the most extensive outing of his career. Smith last missed a game due to injury in 2010 after separating his shoulder against Carolina.
Smith will have to pass a battery of tests and be cleared by an independent neurologist before being cleared for practice. The good news for the 49ers: They have a longer-than-normal work week due to their upcoming game with the Bears on Monday Night Football.
-- Matt Barrows