The San Francisco 49ers will start Brandon Allen at quarterback Sunday against the Green Bay Packers in place of an injured Brock Purdy, coach Kyle Shanahan said Friday.

Shanahan said star defensive end Nick Bosa also will miss the game with injuries to his left hip and oblique. Left tackle Trent Williams is questionable with an ankle injury and will be a game-time decision.

This will be the first time Purdy has missed a start because of an injury since taking over as the 49ers’ quarterback in December 2022.

Allen has started nine regular-season games since entering the league as a sixth-round pick of the Jacksonville Jaguars in 2016. Three of those starts were for the Denver Broncos in 2019, with the other six for the Cincinnati Bengals in 2020 and 2021. He has been with the 49ers since 2023 and has yet to start a game in San Francisco but has been running the scout team against the defense for much of that time.

Purdy, who is dealing with soreness in his right (throwing) shoulder, has been limited in practice this week. He first appeared on the injury report Monday when Shanahan discussed injuries coming out of Sunday’s loss to the Seattle Seahawks. Shanahan said then that Purdy would be considered day-to-day because of the shoulder injury.

Joshua Dobbs will be the backup on Sunday.

ESPN’s Nick Wagoner and The Associated Press contributed to this report.