Report: 49ers DE Nick Bosa suffered season-ending torn ACL

The 49ers' standout pass rusher went down after a third-down play and was evaluated on the sideline and inside the blue medical tent before heading to the locker room. Shanahan said after the game that he did not yet know the extent of Bosa's injury, but didn't rule out the possibility of a torn ACL.

"The MRI also showed that no other ligaments were damaged or stretched a source adds. The medical team believes it should be a clean surgery and recovery," The Athletic's Dianna Russini added.

Veteran left tackle Trent Williams admitted Bosa's absence weighed heavily on the team, even as the offense pieced together a game-winning drive in the closing minutes.

"Anytime you lose a guy like Nick, and he doesn't come back, and his status is unknown, it's a real buzzkill," Williams said after the game.

Linebacker Fred Warner echoed the sentiment, noting that overcoming injuries has become an unfortunate reality for the 49ers.

"Unfortunately, we know too well about guys going down and next-man-up mentality," Warner said. "Other guys had to fill in and play big-time minutes for us and find a way to get the job done."

Williams added, "But it's cliché to say it's a next-man-up league when you lose a guy like that. You need three or four guys to come and fill those shoes. I think we've got the depth, and we've got the youth, so hopefully, they can continue to improve."

Bosa finishes the season with 17 tackles (four for loss), three quarterback hits, two sacks, two forced fumbles, and a fumble recovery through three games. The 27-year-old, a former first-round draft pick, was in his seventh NFL season and is considered a cornerstone of the 49ers' defense.