Former world heavyweight champion Ken Norton passed away at a care facility in Arizona on Wednesday at the age of 70, having suffered congestive heart failure.
Norton was a much respected and popular figure in the boxing world and historian Bob Meed described his incredible talent in an era full of greats.
"It's a sad day, he was a real unsung hero," said Mee.
"Norton's great moment was when he broke the jaw of Muhammad Ali the first time they fought in San Diego 40 years ago and he went on to win a split decision which was a complete shock at the time."
Sky Sports pundit Glenn McCrory says that Norton would have been a match for any heavyweight fighter in this era.
"If you put him in today's era he would be heavyweight champion of the world - he was that good. He came from the greatest era of heavyweight boxing and to beat Ali and take Larry Holmes that close shows what he was.
"The fight against Holmes was one of the greatest i've seen. He gave two of the greatest heavyweight fighters of all time struggles and managed to beat Ali.
"It is a sad passing when someone from that era goes. They're the greats that you grew up with."
Ringside host Johnny Nelson described Norton as a 'fighter's fighter - old school' and added: "I remember him being Ali's bogeyman.
"His style was unconventional, but he was aggressive and very athletic. He could give you nightmares in the ring."