From reading his book and watching his interviews, it was getting to the point were he was breaking his hands nearly every single fight, and every time they broke it meant he had to put less power in his punches for the next fight.
He was once told that he would never box again and went for 3 fights in the early 2000s without sparring, hitting a heavy bag or doing any padwork. By 2008 he basically knew his body was letting him down so he knew Jones was going to be his last fight.
He chose someone who he had tried to fight 10 years earlier but it couldn't be made, and had the fight on the grandest stage of all at Madison Square Garden. If his hands weren't so brittle and he could use them to knock people out like he did in the 90s he may very well have carried on past 50-0. I still think he would have murdered Dawson at light heavyweight.
Joe Calzaghe said, long before doing so, that he would retire at the time he did. I know some here are hard on Calzaghe because he didn't fight many top fighters in their primes. However, some guys actually enter the sport with a purpose and a goal. Once that goal is reached, the said fighter just might not see a purpose in continuing. I think this was the case with Calzaghe. He just didn't see the need to fight once he reached his goals.
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I believe Salvador Sanchez viewed boxing the same way. He never did fit into the mold of the great Mexican warrior, though -in his short time with us- he was indeed a great fighter. Sanchez' dream was to be a doctor. Had he not passed on, the result of a terrible auto accident, he would likely have fought only three more years, after facing -and likely beating- Alexis Arguello for the lightweight title.
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For some guys, finished means just that............finished.
Probably his new found social habit interfered.
Cocaine is a hell of a drug.
Just to beat Sven Ottke's record of 21 defenses.