Brock Purdy participated in the start of Thursday’s practice with the 49ers but the San Francisco starting quarterback was not on the field for the majority of the workout, casting doubt over his availability to play Sunday at Green Bay.

Purdy is dealing with a right shoulder injury and the 49ers are also potentially without left tackle Trent Williams and Nick Bosa due to injuries. Bosa was listed as out of Thursday’s practice with an oblique injury. Williams also didn’t suit up Thursday. He played through an ankle injury last week after being listed as questionable.

Purdy’s typical Thursday post-practice media session was scrapped until Friday as the 49ers did not make any quarterback available. Kyle Allen would step in for Purdy as the starter if he can’t play against the Packers.

Run game coordinator Chris Foerster said the 49ers aren’t where they want to be at 5-5 because they haven’t won close games, not because of injuries.

“Seven games left is like an eternity,” Foerster said. “So much can happen. Do the math. What was our record last year? It was 12-5. I was on a 13-win team that was nowhere near as good as the team last year.”

With or without Purdy, Foerster said the challenge for the 49ers is not to give up the ball to a defense that has 19 takeaways.

The 49ers have 13 giveaways this season.