49ers' Brock Purdy practices fully after concussion diagnosis, could play against Bengals

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Although Brock Purdy still has to clear one more hurdle to clear the NFL's concussion protocol, the second-year quarterback was listed as a full participant for Friday's practice.

Purdy has passed four of the league's five steps in the concussion protocol. 

He reportedly experienced symptoms on the San Francisco 49ers' flight back to California late Monday night. Purdy's progress has increased optimism about his availability to play in the Niners' game against the Cincinnati Bengals Sunday.

The 23-year-old quarterback is officially listed as questionable for Sunday.

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Brock Purdy of the San Francisco 49ers against the Minnesota Vikings in the first half at U.S. Bank Stadium Oct. 23, 2023, in Minneapolis. (David Berding/Getty Images)

Purdy appeared to take a hard hit to the helmet late in Monday night’s loss to the Minnesota Vikings.

Purdy participated in a portion of a walkthrough Wednesday, was limited in practice the next day and was a full participant Friday. Niners head coach Kyle Shanahan said Purdy will start if he clears the protocol. Otherwise, Sam Darnold will get the nod.

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"That's the last thing he's got to do," Shanahan said. "Just one step left. ... He was full go today; he's just got to pass that tomorrow."

To clear the fifth and final step of the league's concussion protocol, Purdy will have to be cleared for full contact by the team's doctor. A neurological consultant must also examine the quarterback. Once the team physician and an independent consultant