Brock Purdy practices on Thursday; Trent Williams remains out

Sam Darnold will take practice reps with the starters on Thursday. That’s largely because 49ers starting quarterback Brock Purdy hasn’t been cleared from the concussion protocol yet.

According to the beat reporters on hand, Purdy participated in individual drills, which is a good sign that Purdy isn’t suffering from concussion symptoms and is on track to play Sunday against the Cincinnati Bengals.

There are five stages of the NFL’s concussion protocol. If Purdy hadn’t cleared the first three, then he wouldn’t be practicing. Stage four is called “club-based non-contact training drills,” which is what Purdy is taking part in during Nick’s video from above.

Here’s a description of the fourth stage of the NFL’s concussion protocol:

Players reaching the fourth stage are able to start throwing, catching and running and engage in activities more specific to their position. They also can continue to ramp up their exercise and training. By end of this phase, players have to have undergone neurocognitive and balance testing.

Purdy must be cleared by the 49ers physician and an independent neurological consultant to return to full activity. Once that happens, Purdy can practice during full team periods.

Trent Williams wasn’t spotted at practice, per the reporters present. Deebo Samuel remains out with a shoulder injury.

Here’s Shanahan on Williams’ availability from Wednesday:

“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.”

Because the 49ers played on Monday, Shanahan was saying that a short week wouldn’t have been worth the risk of playing Trent. Although playing on Minnesota’s surface would have helped.