San Francisco 49ers star defensive end Nick Bosa reportedly will undergo season-ending surgery after suffering a torn ACL against the Arizona Cardinals on Sunday, according to ESPN's Adam Schefter. ▶️ Full Cardinals-49ers Recap 04:04Losing Bosa is a huge blow to the 49ers' defense. San Francisco came into the season knowing it would be without wide receiver Brandon Aiyuk for a while as he recovered from a torn ACL. The 49ers then lost George Kittle due to a hamstring injury in Week 1, and he's currently on the injured reserve. Wide receiver Jauan Jennings is also sidelined because of shoulder and ankle injuries.