For anyone who doesn't click the links in posts, Knox is an Augusta resident and member of the National who is in his mid-50's now I think. He's always played as an amateur, winning the Georgia Mid-Am three times and finishing 2nd in the Georgia Amateur as well. Several pros ask to play practice rounds with him to pick his brain about course strategy, reading the greens, Masters setups, etc.
He's beaten Rory twice, and beat Sergio so badly a couple of years ago that Sergio wouldn't shake his hand afterwards. I would imagine Sergio was just mad about finishing dead last, but still...c'mon man.