A fully-torn MCL is pretty damn hard to hide, so I am calling partial BS on this.
I had a fully-torn MCL and, with any sudden lateral movement, the knee bends in half sideways, like an open book closing, and I fell to the floor.
He would have to have been extremely lucky to not feel any lateral movement during games when pass rushers were trying to kill him.
The one thing that he had going for him with a fully-torn MCL is that there is zero pain.
I remember going to the doctor's office after the injury. He asked me if I felt any pain, as he held my knee with his left hand and moved my foot to a 90 degree angle sideways.
When I said no, he said, "OOOOHHH! That's bad!".