It's very early so we don't know the circumstances around his injury nor the "extensive injuries" to other team members, but this quote implies that it's to his other knee.
I'd just like to throw out there that I had an entire write-up here on the importance of the Strength Coach (Feld) in regards to non-contact knee injuries and how we should keep an eye on the knee injuries here since it was one of the things Oregon was plagued with during his tenure. It is highly correlated with a lack of knee-flexion hamstring development. I'll pull receipts if I have to.
We don't know if it was a non-contact issue but as we get more data in from these injuries, if it appears that more and more of them are related to knee / ACL issues, I'm going to look like a god **** savant and maybe you guys will start listening to me. Everyone loves the before/after pictures but then when half of your RBs are out with ACL tears it's just "bad luck."