Sep 21, 2025; Santa Clara, California, USA; San Francisco 49ers defensive end Nick Bosa (97) on the field during warm ups prior to a game against the Arizona Cardinals during the first half at Levi's Stadium. Mandatory Credit: Cary Edmondson-Imagn Images

The San Francisco 49ers need a big Thursday night win over the Los Angeles Rams to stay afloat in the early NFC West division race. Unfortunately, they'll have to do so without starting quarterback Brock Purdy, along with arguably his top two weapons in receivers Ricky Pearsall and Jauan Jennings.

Even worse, they're going to be without superstar pass-rusher Nick Bosa, too. And not just for this game.

If you're just getting caught up on the 49ers' season and wondering why Bosa isn't suited up to play against the Rams, that's because he tore his ACL during the 49ers' Week 3 over the Arizona Cardinals. Bosa will, in fact, miss the rest of the 2025 season as he recovers. Oof, brutal:

Needless to say, Bosa's absence is a huge deal for a 49ers team already dealing with a rash of injuries on both sides of the ball.

The 49ers didn't necessarily miss Bosa from a pass defense perspective in their Week 4 loss to the Jacksonville Jaguars. Jacksonville quarterback Trevor Lawrence managed just 174 yards and one passing touchdown. It's not like he was lighting it up. The 49ers did, however, likely feel the lack of Bosa against the run as the Jaguars amassed over 150 team rushing yards while averaging over five yards per carry. Bosa is obviously known for his pass-rushing ability, but that doesn't make his elite ability to set the defensive edge against opposing teams' rushing attacks any less important. He does so much for the San Francisco defense with his presence alone.

So, yeah. Bosa is out Thursday night and for the rest of the 49ers' season. That's not great! We'll see how they manage over the next few months without arguably their best player.

This article originally appeared on For The Win: Why isn't Nick Bosa playing Thursday night?

Reporting by Robert Zeglinski, For The Win / For The Win

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