Nick Bosa Ruled Out as 49ers’ Defensive Line Crisis Reaches Breaking Point: Details Emerge

Nick Bosa has hit another setback, and this one leaves San Francisco with a much thinner defensive line. The five-time Pro Bowler pulled his calf during Thursday’s practice and is officially out for Sunday’s game against Arizona.

The timing hurts because Bosa had just returned from the torn ACL that ended his 2025 season. He played 63 percent of San Francisco’s defensive snaps through two games before the calf problem surfaced, while several other defensive linemen have already gone down.

Nick Bosa will miss multiple weeks

ESPN’sAdam Schefter andIan Rapoportreported Friday that Bosa is expected to miss “a few weeks.” The team is also deciding whether to place him on injured reserve. San Francisco later listed Bosa as out on its final injury report.

Five-time Pro-Bowl DE Nick Bosa pulled his calf during Thursday’s practice and now is expected to miss “a few weeks”, including Sunday’s game vs. the Cardinals, sources tell me and @RapSheet. The team is figuring out whether or not Bosa needs to be placed on injured reserve. pic.twitter.com/eQIb7JBKut

— Adam Schefter (@AdamSchefter) September 25, 2026

The injured reserve decision matters because Bosa would have to miss at least four games before returning. With San Francisco already short on defensive linemen, that absence could affect the team’s rotation through October.

Bosa suffered the injury during an individual warm-up rather than a contact play. The timing makes the setback more difficult after the 49ers carefully managed his return from the torn ACL that ended his 2025 season.

Concern grew Thursday night after Bosa missed his expected media availability for a second straight day. During an NBC Sports Bay Area livestream, Jennifer Lee Chan said her “spidey senses” suggested the injury could be serious and keep him out for several weeks. Friday’s report provided a clearer timeline, but it did not bring better news.

Kyle Shanahan has a bigger problem to solve

Kyle Shanahan must replace more than Bosa along San Francisco’s defensive line. Alfred Collins is out for the season, while Sam Okuayinonu and C.J. West are on injured reserve. James Thompson Jr. is also expected to miss time, and Romello Height had hand surgery this week.

“Losing Bosa was rough yesterday,” Shanahan told reporters. He added that San Francisco had already lost six of the 10 defensive linemen who made the team during the first two weeks. That number shows why Bosa’s absence affects more than one position in the rotation.

The 49ers have started adding help. They signed Naquan Jones and Viliami Fehoko Jr. to the practice squad and promoted Ogbo Okoronkwo earlier this month. Those moves give Shanahan more options while the team rebuilds its defensive line.

Mykel Williams could provide another option soon. He has been working toward a return and could begin practicing next week.

Bosa is expected to return within a few weeks, so the injury is not expected to end his season. Until then, San Francisco must face Arizona without its top pass rusher while managing a defensive line that has lost several players.

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