The 49ers earned a win on Sunday but their defense suffered a notable blow in the process. Defensive end Nick Bosa went down with a knee injury during the contest and did not return. 
At this point, a clear diagnosis is not in place. The initial fear was an ACL tear, although head coach Kyle Shanahan said (via Matt Barrows of The Athletic) that has been ruled out. Further testing will take place on Monday.
“We can’t rule everything out,” Shanahan added (via Cam Inman of the San Jose Mercury News). “They checked [Bosa’s] ACL and it was good with that. But we have to check on everything.”
That is an encouraging first sign, although Shanahan later clarified an ACL injury other than a tear could still be possible (h/t ESPN’s Nick Wagoner). A serious injury affecting Bosa’s knee would of course be crippling to San Francisco’s defense, a unit which currently ranks third in the NFL in points allowed and fourth for yards surrendered. It would also mark the second time Bosa, 27, has been forced to miss considerable time in a season.
The former Defensive Rookie of the Year was limited to just two games during his second NFL campaign. Bosa managed to remain healthy (largely speaking) since then, however, playing between 14 and 17 games over each of the past four years. The five-time Pro Bowler saw a downturn in production with nine sacks in 2024, but he has already posted two in the early stages of the current campaign.
Adding to that total would help allow for the 49ers’ defense to remain among the league’s best. Without Bosa – who is attached to a $34MM-per-year extension – for a long period, though, San Francisco’s 3-0 start to the campaign would be undone to an extent. Further clarity once follow-up tests take place will be worth watching for during the day.
I’m so sad