They changed their styles

Ruben Olivares, who was such a complete fighter, but is known primarily as a banger. Watch his rematch with Art Hafey. He turns complete boxer for this one after suffering a KO to Hafey in an earlier bout. By this stage of his career Ruben wouldn't take 'unimportant' fights seriously and paid the price several times, yet, would whip himself into pristine condition when it mattered. He was ready for this rematch and became the matador in this one. I never really saw the controversey in this bout. He was dropped in the 10th by Art, but I had him comfortably ahead in a fantastic performance in a style that I did not expect.

 

Hagler turned into an aggressive bull against Hearns

Duran added tweaks as he got older. There's a pretty noticeable difference in speed once he was above 147, due to the natural changes brought about by age, having a ton of lot of fights, and possibly his own bad habits. You could see he was more methodical and cerebral and fought at a more deliberate pace.

 

Barrera

 

I was über impressed when Hearns showed skills ala his 1st fight with Leonard.

 

Floyd?

He was a bit of a banger and had tremendous killer instinct south of 147. Now he NEVER goes for the kill and is basically a point-fighter.

 

Yeah Hagler could box or brawl depending on the fight. Though he was the most complete fighter I've seen.

Barrera defo a good shout.

Too a lesser degree Nigel Benn. Went from purely a banger at mw to becoming a cuter operator at smw after defeats and not carrying the same power that he did at mw. Still the same Benn but with a little more thought.

 

Hopkins came to mind first. He went from an aggressive, seek and destroy pressure fighter to a cute, slick counterpuncher.

Also while i'm at it Andre Ward went from an athletic Roy Jonesish style to a more technical Hopkinsish style.

 

Evolution in style is often the key to longevity in boxing. Conditioning can only go so far when reflexes and reaction times fade. George Foreman wrote that once this happened to Ali, it became apparent he never really learned defense, and that toughness was actually his ticket through much of the 1970's.

I think Foreman was more a case of reverting to his jab oriented Olympic days for his second career. Also, always bouncing a bit on his feet during his youth, he became much more flatfooted, sparing his legs while retaining his corner cutting efficiency. He also worked harder in training than he did in competition. During his first career, George never produced a knockdown later than the round fives in Lyle and Frazier II. As a mature athlete, he retained that power into double digit rounds.

Larry Holmes tried to fight Tyson as if he was still in his 20's, but for his final comeback, he admittedly adapted the Foreman template to use his legs less, then suckered Ray Mercer into the corners to outwit him in a way which I think would have given George nightmares in Kinshasa. (For me, the priceless moment in Holmes-Mercer was when Larry, in a corner, grabbed the rope with his right hand and used it to slip the punches Ray was flailing away with.) He didn't take anything resembling the face damaging beatings Foreman withstood from Stewart and Moorer, but actually clowned and played with Mercer as he won the crowd over, chanting his name.

Off-hand, I think the biggest change in style I saw while I was following boxing was when Hilmer Kenty abandoned his foot speed and converted to stalker for his electrifying WBA LW Title win against jaw breaking hooker Ernesto Espana (an outcome which ruined the lethal Espana), becoming Manny Steward's first world champion. It caught up with him against a prepared Sean O'Grady as it inevitably was going to, but that unnaturally aggressive style did make him more exciting and got him on network television through the entirety of his reign. We only saw him revert back to his natural stick and move speed orientation against John John Molina after he lost the title. Steward's been criticized for changing Hilmer from his natural style for his title run, but maybe Kenty would not have become noted without that change.

Manny Steward also converted Hearns into a puncher from his days as a feather fisted amateur. Tommy was always a stylist first by origin. His inability to clinch was fatal in SRL I, but after he was decked in round four by Kinchen in November 1988 he'd proved he'd mastered holding so effectively that referee Mills Lane deducted him a point for refusing to let go. Gerry C00ney never learned to clinch, and Michael Spinks made him pay dearly for it.

Galindez remains unique for his brand of what one scribe called, "steel chinned guerrilla warfare." He was no kind of slick Benitez off the ropes, but more like Foreman would have been in Kinshasa if he traded places with Ali against those ropes. Countering to the body off the ropes would be suicidal for most, and his is a case where O'Grady's old chin-cash register anecdote you recently repeated does authentically hold up. Marvin Johnson could be cited as a case of Victor being weight drained and no longer able to make 175 with sufficient strength left, but his career finale rematch against Jesse Burnett in a bid to extend his boxing life into the newly created CW division proved his chin was gone, and he did well to last the 12 round limit in that title eliminator.

 

Ali went from dancing in the 60's to neck pulling in the 70's.

 

Juan Manuel Marquez

 

Would Ezzard Charles count???

 

And Archie Moore, in Foreman's corner for Kinshasa, specifically cited that tactic as the one which drained George to the point he was weakened enough to be knocked out.

The Ole Mongoose wasn't complaining, simply reporting the facts as he witnessed them. Of course neither Foreman or Ali were choir boys at the altar, and Ali was simply the better cheat with his neck puling than George was with his shoving and kidney punching.

For Ali's first title defense, there was some karmic justice as he experienced the targeting of his own neck with rabbit punches from Chuck Wepner, to the point he was actually blocking those shots by placing his hand behind his head. (Wepner was then the biggest contender in boxing at 6'5" and uniquely had the height to literally go over Ali's head like that.)

Carlos Padilla's name was made when Cosell repeatedly praised him for denying Ali the use of that tactic in Manila, forcing him to win with more than sleight of hand.

 

Miguel cotto is a great example when he was at 140 he was almost a one dimensional slugger then when he moved up and his power wasn't as prevalent he became a much more rounded boxer culminating in his amazing chess match with Floyd
it was a highly competitive fight that wouldn't have been nearly as competitive if cotto had fought like he did in the beginning

 

What most impressive to me, is doing during the fight itself. Ali quickly realized he would not be able to move for 15 rounds, so the rope a dope developed. Leonard realized he was getting picked apart from the outside against Hearns, he became a body punching slugger. Hagler probably realized his best chance with Hearns was to crowd him and limit his punching room. Pryor realized during fight with Arguello he would not be able to just run him over. So he boxed the middle rounds. Some off the top of my head.