Already without their starting quarterback, the San Francisco 49ers also will be without star left tackle Trent Williams, who was ruled inactive for Sunday's game against the Green Bay Packers.
San Francisco waited to make a decision on Williams, wanting to see how his injured ankle felt in pregame warmups.
Veteran quarterback Brandon Allen will make his first start in more than two years in place of the injured Brock Purdy (shoulder).
Williams, who was listed as questionable, did not practice this week after playing through his injury in last Sunday's home loss to the Seattle Seahawks.
The 49ers believe Purdy should be able to return next Sunday against the Buffalo Bills despite his shoulder soreness, sources told ESPN's Adam Schefter. The Niners, however, also thought Purdy would be able to start Sunday against the Packers despite his injury, and he couldn't.
For the time being, there does not seem to be a high level of concern for Purdy's injury, sources told Schefter.
The Niners (5-5), who are fighting to stay in the postseason hunt, also have ruled out star pass rusher Nick Bosa, who is dealing with injuries to both hips and obliques.