SANTA CLARA – Doctors examined 49ers quarterback Alex Smith for a concussion six plays before he dove head-first into a pile of players and emerged with blurred vision, coach Jim Harbaugh said Monday.

Smith eventually left Sunday's game with a concussion, and he saw a neurologist Monday afternoon, the first step in the NFL's more stringent protocol for dealing with head injuries.

"(He's) doing much better, had a good night's sleep last night," Harbaugh said. "And symptoms are positive today."

Smith absorbed at least two big hits during a 12-play drive that spanned the first and the second quarters. On the first, he slid awkwardly after a short scramble and was struck in the back of the shoulder and the helmet by Rams linebacker Jo-Lonn Dunbar. Smith seemed to get up slowly after the play, and team doctors – presumably between quarters – examined him for signs of a concussion.

"That was a good-sized hit," Harbaugh said during his Monday news conference. "Our doctors were good; they were very pro-active on that hit. They watched it on the monitors, and Alex had no symptoms after that hit. He was cleared to play."

On the same drive, Smith dove into the pile on fourth and one, and he later reported to 49ers officials that he emerged with fuzzy vision.

It didn't seem to affect him on the field. He played five more snaps on the drive and threw two darts to Michael Crabtree, one of which the wide receiver ran into the end zone to cut St. Louis' lead to 14-7.

When he got to the sideline, however, he told Harbaugh he was having trouble seeing.

"What he expressed was, he came up and said he had blurred vision, and he felt that it would go away," Harbaugh said. "And he came over to the sideline and sat down and felt like it was something that would go away, but it didn't. So he told me he had blurred vision, and that's when we made the move."

Said Harbaugh of the earlier hit by Dunbar: "There's no telling whether that earlier hit contributed. I don't think Alex knows for sure, either."

Smith was not available for comment after the game per NFL concussion protocol, and no players were on hand Monday.

Before returning to practice, Smith must be cleared by an independent neurologist, who will compare baseline cognitive tests Smith took during the offseason with data taken this week. Once cleared, he must go through a non-contact practice before rejoining the full session.

Harbaugh would not offer a deadline by which Smith would have to be cleared if he is to play against the Bears on Monday.

That game could be a battle of backups – Colin Kaepernick against former Raider Jason Campbell, who relieved Chicago starter Jay Cutler after he suffered a concussion Sunday.

Harbaugh gave Kaepernick high marks from Sunday, especially considering it was his first extended NFL outing and that he entered with the 49ers trailing by a touchdown. The coach also said there were some throws Kaepernick, like any quarterback, should not have made.

Et cetera – Harbaugh revealed that wide receiver Kyle Williams would have played quarterback had Kaepernick gotten hurt Sunday. Third quarterback Scott Tolzien was inactive for the game. Tolzien will be activated if Smith can't play Monday.

• Frank Gore, Mike Iupati and Aldon Smith were among the 49ers who emerged from the 75-minute game with bumps and bruises. But apart from Alex Smith's, Harbaugh said, none of the injuries is considered serious.

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