Brock Purdy’s shoulder soreness is serious enough to keep him out of a massive Week 12 showdown.

Purdy has been ruled out for the San Francisco 49ers’ game Sunday against the host Green Bay Packers. Brandon Allen will get the start for the Niners,

Niners head coach Kyle Shanahan is hoping the shoulder injury will only result on a one-game absence for Purdy.

“I don’t want to say there’s long-term concern, you know we got the MRI on Monday, we thought he just needed some rest and really weren’t concerned about him not being good this week,” Shanahan said. “But when he started up Thursday, it just surprised him, surprised us how it felt. So we had to shut him down, and so I really don’t know what to think of it. The MRI doesn’t look like that, so it should be alright, but the way it responded this week, it’s really up in the air for next week. So we’ll have to see on Monday.”

Shanahan announced this past Monday that Purdy would be day to day due to shoulder soreness. It led to him practicing in limited fashion and peaking concern on Thursday when he left practice early for treatment and didn’t speak to the media, which can sometimes be an indicator as to whether a player will be active or not.

Unfortunately for San Francisco, Purdy’s silence has spoken volumes. Amid his third season, Purdy will miss the first game of his career due to injury.

In addition to Purdy, defensive end Nick Bosa is among 49ers who will also be out against Green Bay.

Through 10 games this year, Purdy has completed 66% of his passes for 2,613 yards, 13 touchdowns and eight interceptions.

Purdy will be replaced under center by Allen. Sunday will mark Allen’s first start since Week 18 of the 2021 season for the Cincinnati Bengals. In his career, Allen has made just nine career starts.

“I think Brandon’s a really good thrower, runs our offense well, has done a really good job since he’s been here,” Shanahan said. “Been here two years now, and guys believe in him and think he’ll give us a good chance to win.”

The 49ers kick off against the Packers at 4:25 p.m. ET on Sunday.