SANTA CLARA, Calif. -- San Francisco 49ers defensive end Nick Bosa will not return Sunday's game against the Arizona Cardinals after suffering a knee injury late in the first quarter.
On the play, Bosa was rushing Cardinals quarterback Kyler Murray from the left side and engaged with left tackle Kelvin Beachum when Cardinals guard Evan Brown came over for the double-team.
Bosa's knee appeared to bend awkwardly as he went to the ground, and Murray's pass fell incomplete. Bosa walked slowly to the sideline, where the Niners' training staff began working on him as he laid on his back.
After a few moments, Bosa walked to the blue medical tent, where he remained for about five minutes before emerging. He spent the next couple of minutes doing some stretching and high knees but eventually made his way to the locker room.
Bosa was spotted giving a thumbs down as he ambled to the locker room. The team ruled out a potential return before the start of the third quarter after Bosa was initially listed as questionable to come back.
San Francisco has again been hit hard by injuries in the opening weeks of the season and were already playing Sunday without tight end George Kittle (hamstring), quarterback Brock Purdy (toe) and receiver Jauan Jennings (shoulder, ankle), among others.
Through the first two weeks, Bosa had delivered in key moments, posting two sacks, eight pressures, 15 tackles, a 21.9% pass rush win rate (15th among ends) and a 38% run stop win rate.
Bosa wasn't the only Niners defensive end to depart in the first half, with rookie Mykel Williams also heading to the locker room because of a wrist injury. But Williams returned to the game just before the end of the first half. Williams, Bryce Huff, Yetur Gross-Matos and Sam Okuayinonu are the remaining defensive end options behind Bosa.