Coach Jim Harbaugh said Monday that Smith connected with Michael Crabtree six plays after he began experiencing blurred vision on a 1-yard keeper early in the second quarter. Six plays earlier, he had taken a vicious hit from St. Louis linebacker Jo-Lonn Dunbar.

Smith scrambled to his left and started to slide before turning when Dunbar got him in the back of the neck with 1:10 left in the first quarter. He briefly grabbed his face mask and grimaced but stayed in the game.

“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.”

Second-year backup Colin Kaepernick entered for the next offensive series after a hurried warm up. Because No. 3 quarterback Scott Tolzien was inactive, wide receiver and special teams player Kyle Williams would have stepped in at quarterback in an emergency.

Harbaugh expressed concern at the thought the 28-year-old Smith played through some concussion symptoms.

“Yeah, that’s something, you don’t want him out there with blurred vision,” Harbaugh said. “We talked about it. What he expressed was he came up from the sneak and he had blurred vision and he felt that it would go away. He came over to the sideline and sat down and felt it would go away and it didn’t. He told me he had blurred vision and that’s when we made the move.”

Harbaugh said the QB improved overnight and would see a neurologist later Monday. His status is unclear for next Monday night’s game against the Bears is uncertain.

“Rather than speculate, we’ll let it play out,” Harbaugh said. “There’s a progression and evaluations that have to be gone through before we’ll really know anyway. … He’s doing much better, had a good night sleep last night, symptoms were positive today. He’ll be visiting with the neurologist later this afternoon that will be the next step.”

Harbaugh, himself a 15-year NFL quarterback in his day, figures he had multiple concussions during his playing career. He appreciates the increased awareness and serious NFL stand on the issue.

“I think it’s a major point of emphasis,” Harbaugh said. “I don’t have a medical degree. I’m confident in the way the doctors, especially our doctors, their understanding of it and their professional opinion.”

Tolzien could be called upon to do more in practice this week as the NFC West-leading Niners (6-2-1) prepare for Chicago’s visit to Candlestick Park in prime time.

“There’s a possibility he could get more reps,” Harbaugh said, unwilling to guess on Smith’s status. “Well, certainly, Dr. Harbaugh won’t be qualifying, quantifying that.”