SAN FRANCISCO -- After successfully converting a fourth-and-1 quarterback sneak, Alex Smith remained in the game for six more plays.
He completed three short passes, including a 14-yard catch-and-run by Michael Crabtree for a touchdown. Then, he reported blurred vision on the sideline just before he was about to re-enter the game, 49ers coach Jim Harbaugh said.
Smith did not return to the playing field in the 49ers' 24-24 tie against the St. Louis Rams on Sunday. He will be required to go through the typical NFL-mandated protocol to be cleared to play next Monday night against the Chicago Bears.
"From what I've been told by the doctors and the trainers it seems like it was the quarterback sneak," Harbaugh said.
Smith also took a big hit from Rams linebacker Jo-Lonn Dunbar at the beginning of Smith's final drive. But it was after the quarterback sneak, during which Smith buried his head into the pile to pick up the necessary yardage, that Smith first complained of concussion symptoms.
"He said he had the blurred vision after the quarterback sneak," Harbaugh said. "There's no telling. Did that earlier hit contribute? I don't know. I don't know Alex knows for sure, either."
When the 49ers took the field for their next series, Colin Kaepernick entered the game.
When asked if Smith's injury took something out of the 49ers, left tackle Joe Staley said, "I mean, that's our starting quarterback. That's our guy. Any time your starting quarterback goes down, it stinks a little bit. But we have a lot of confidence in Kaep. He takes reps in practice and he knows this offense."
Smith completed 7 of 8 passes for 72 yards and a touchdown. Kaepernick completed 11 of 17 passes for 117 yards. He also ran eight times for 66 yards.
The 49ers did not have a No. 3 quarterback in uniform. Scott Tolzien is the 49ers' third quarterback but he was declared one of the team's seven inactive players.
Nobody seemed to know who would've entered at quarterback if a replacement were needed for Kaepernick. Crabtree, who played quarterback at David W. Carter High School in Dallas, said he "hopes" he would've gotten the call, if needed.