Gurley already had an ACL tear in his history. SJ didn’t.
Arthritis is a very common side affect that goes with any joint, tendon, or ligament surgery, or at least that is what my Orthopedic surgeon has told me. He also told me that the harder I am on it the sooner I’ll see arthritic symptoms arise My brother had knee surgery and so did my wife ( division 1 goalie). Even in their younger days there is no way they could have played runningback for too long.
So even if Gurley plays for years, it isn’t likely that he can play at the same elite level that he was paid to play at.