Óscar Rivas vs. Carl Drumond

Okay, so Drummond is clearly no blood and guts warrior, but having watched it again, I think it may indeed have been a legitimate KO. The first real power shot Rivas lands is that high kite-flying windmill of a right hand that appears to land behind the ear of Drummond. That is probably the one that sapped his equilibrium and from which he never fully recovered. Not much else clean got in during Rivas' follow-up, except that last straight right hand about 53 seconds into the round, the final blow landed before Drumond collapsed, was seemingly pretty flush & hard.