Brock Purdy, Nick Bosa both out against Packers, putting 49ers’ season in peril

The 49ers are in a world of hurt entering this Sunday’s game against the Green Bay Packers. The team officially ruled out quarterback Brock Purdy and defensive end Nick Bosa, its most important players on both sides of the ball, before flying to Wisconsin on Friday afternoon.

Veteran Brandon Allen will start in place of Purdy against the Packers. Josh Dobbs will be the 49ers’ backup.

Purdy suffered a shoulder injury in last week’s loss to the Seattle Seahawks. He underwent an MRI on Monday that returned encouraging results but had to exit Thursday’s practice after struggling through some warmup throws.

“We thought he just needed some rest and really weren’t concerned about him not being good this week,” 49ers coach Kyle Shanahan said Friday. “But when he started up Thursday, it just surprised him, surprised us, how it felt.”

Purdy and the 49ers aren’t sure of when exactly he sustained the injury against Seattle. He did have five scrambles, including a diving touchdown run, and the Seahawks did hit him four times.

“He said he had a hard time keeping it loose and then after the game is when it really started to hurt,” Shanahan said. “And then Monday morning is really why he had to go get an MRI for it.”

Allen, who’s been with the 49ers for the past two seasons, will be making his 10th career start. Allen was previously Joe Burrow’s backup for the Cincinnati Bengals, where he managed passer ratings of 99 or above in three of his nine starts.

Can the 49ers realistically expect the 32-year-old Allen to deliver an efficient game against the Packers? A key part of their hope might lie in Green Bay’s recent defensive struggles. The Packers, although they rank No. 10 overall in expected points added (EPA) on that side of the ball, have ranked No. 29 over their past three games. Allen’s three best career starts have all come against defenses ranked No. 22 or worse — so it’s fair to question which version of the Green Bay defense will show up Sunday.

“It’s an opportunity,” Allen said Friday. “The circumstances are what they are, but I think our team — all year long— we’ve been kind of dealing with injuries here and there, and it’s been a big next-man-up mentality.

“So it’s definitely an opportunity for me to go out and play well and put our guys in a good position to win the game. And obviously, we want Brock back and healthy and all that, but for the time being, it is an opportunity for me.”

Allen has played under Los Angeles Rams coach Sean McVay and Bengals coach Zac Taylor, both of whom run offense with commonalities to Shanahan’s. He beat out Dobbs, who’s a better runner but also newer to the 49ers’ system, for the backup quarterback spot in the preseason.

There’s also a chance that Allen with have to work without starting 49ers left tackle Trent Williams, who’s officially listed as questionable with his ankle injury. Williams strained through the injury against Seattle but was again unable to practice this week. Jaylon Moore is Williams’ backup.

The loss of Bosa, who’s listed with a hip and oblique injury, is also problematic for the 49ers. The NFL’s 2022 defensive player of the year suffered the injury on his second sack of Seahawks QB Geno Smith last week. The 49ers struggled mightily without Bosa on the field, allowing about 6 yards per play and both of Seattle’s touchdowns.

Defensive end Yetur Gross-Matos, who had one sack in his return from a knee injury last week, will likely start in Bosa’s place opposite Leonard Floyd in Green Bay. It’ll be up to 49ers defensive coordinator Nick Sorensen and his staff to scheme up pressure against Packers quarterback Jordan Love, who has thrown 11 interceptions already this season — good for the third-worst interception rate (4.3 percent) in football.

Sorensen has blitzed only about 16 percent of the time, the second-lowest rate in the NFL. The 49ers might have to raise that number to compete without Bosa coming off the edge.

Either way, they’ll need to defy odds to win in Green Bay and avoid a position of absolute desperation in the standings. Most of that onus will fall on the arm of Allen, who’ll be tasked with distributing the football to Christian McCaffrey, George Kittle, Jauan Jennings, and Deebo Samuel — the 49ers’ stars who will actually be available in this game.

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