The San Francisco 49ers could well have a different quarterback for the visit of the Cincinnati Bengals after it was revealed Brock Purdy is in the concussion protocol.

Purdy faces an uphill battle to play against Cincinnati having first started showing concussion symptoms on the flight back from Monday's 22-17 loss to the Minnesota Vikings, meaning Sam Darnold looks set to deputize as the Niners aim to snap a two-game losing streak.

Aside from Purdy, there were no new additions to the injury report, with head coach Kyle Shanahan expressing some optimism a starter who missed the defeat to Minnesota will return this weekend. 

49ers Injury report

Injury report observations

The 49ers had a walkthrough on Wednesday and Kyle Shanahan said Purdy could participate in that, with Darnold getting the first-team reps in practice in his absence.

Trent Williams does not normally practice on Wednesdays and today was no exception for the All-Pro left tackle who missed the defeat to Minnesota with an ankle injury.

San Francisco's offensive line struggled mightily in both run blocking and pass protection without Williams, though his stand-in Jaylon Moore was far from the worst offender against an ultra-aggressive Vikings defense.

And Shanahan raised hope Williams will be able to return to the lineup for a matchup with a talented Bengals front, indicating that he could be back in practice on Thursday.

Shanahan, indicating that the playing surface at the Vikings' U.S. Bank Stadium went into his absence on Monday, said:

“Yes, the surface and the quick turnaround. I think Trent could’ve been out there. We don’t know if he would’ve made it through it and he wouldn’t have been out there close to 100 percent. He probably wouldn’t have made it through it and that would’ve meant he had no chances this week. So, hopefully he has a better chance to get there this week."

Williams returning to the fold would not only be a boost for Darnold, but also for do-it-all running back Christian McCaffrey, who after shaking off an oblique injury to score twice against the Vikings, was a full go in practice on Wednesday. 

Though he extended his streak of touchdowns from scrimmage to an NFL record 16 consecutive games, McCaffrey averaged just three yards per carry as Minnesota dictated the line of scrimmage. Williams reassuming his role as the starting left tackle would go a long way to solving the 49ers' issues up front.

McCaffrey will tie the all-time record for successive games (including postseason) with a touchdown should he score against the Bengals.

Deebo Samuel remains out with a hairline fracture in his shoulder. The 49ers are hopeful he can return after their Week 9 bye.

Talanoa Hufanga calls out lack of effort after 49ers drop second straight to Vikings

He was blunt in identifying the problem.