USC linebacker Porter Gustin reportedly suffered a knee injury during the first week of fall camp that will require surgery, keeping him sidelined for an undetermined amount of time. 

The Orange Country Register reported Wednesday that Gustin suffered a torn meniscus in his left knee on a non-contact play in practice. Reporters asked Helton after practice about the severity of the injury, which required Gustin to be carted off the field. 

"We are going to have to see the MRI," Helton said, via 247Sports. "Let me wait to get the MRI before I start guessing to what it is. But they did feel that it was stable. 

"It's very tough, you are talking about one of the leaders on your football team and a great player. You catch your breathe, say a prayer for him and quick health, it's not being too serious. I don't know if there is anybody that has worked harder to be ready for this season on our football team and I'm hoping God hears those prayers and he's ready to go when he's back to 100 percent."  

When healthy, Gustin has been one of the Trojans' top defensive players. Last year he was limited to just four games because of a fractured toe and a torn bicep. In 2018, at full health, Gustin was set to be one of the top pass rushing threats in the Pac-12.