My problem is not that the shot landed. It did.
I question whether or not the shot landed before the injury. At the same time, or after the injury. Hard to know exactly when the knee gave out.
Mostly though I question whether Nganouu finishes Cain after the shot lands regardless of Cain getting injured or not. That's what I cant determine, it is pretty clear the shot lands, but the impact of it, whether it was a fight stopping punch, or whether Cain recovers without that injury taking place.
That I dont really know. Since Francis hits like a truck you could give him the benefit of the doubt, but its hard to except as a Cain fan that he could get stopped by a punch like that.