I think he had a better chin than Graham, who was past his best by the time he fought Jackson - even though he was winning easily until about a second before that right hook landed.
This would be brutal and abrupt... Oscar was never as clever a boxer as people made him out to be. and the only way to kill off a prime Jackson was to out fox him with dark arts like McCallum or out gun him like Gerald.... Oscar couldnt do either with a rampaging Jackson.... Jackson!! very early!!!