The bout wasn't even a minute and a half old when Povetkin landed a powerful right hand straight to Perez's chin.
Perez - who hadn't even looked like landing a punch in a boring 90 seconds - hit the canvas. Hard.
The Cuban struggled to his feet and looked wobbly once he got there.
Referee Massimo Barrovecchio decided to let Perez keep fighting even though he didn't seem to be responding.
Watch the punch and see Perez drop to the mat.
Now here's Perez getting to his feet and the ref telling him to fight on.
You can almost see Perez looking at Barrovecchio and asking "are you for real??"
It's hard to tell whether Povetkin's punch actually ends the contest, or if Perez was simply so off balance that he fell into the ropes.
So should the ref have stopped it with Perez clearly dazed, or was he fine to fight on considering he'd regained his feet?