Clear Symptoms of aging(less movement more holding/spoiling), or simple improvements dont count. Only major stylistic changes AFTER a fighterhad already established himself as a top fighter and attained some measure success, standing or fame. So tommy hearns turning from a pure boxer in the Ams to a stalker doesnt count either. Example: Winky shelling up and walking opponents down Hopkins turning into a circling, cautious ambush fighter from an aggressive almost brawler type Gatti boxing more after teaming up with McGirt Foreman completely overhauled his style, from aggressive brawler to a behind the jab stalker in his comeback. Miguel Cotto kept alternating between boxer and pressure fighter.
Finally, the thread I've been waiting for (thank you Contro)...and I was going to start one of this subject myself, believe it or not. First of all, Victor Galindez comes to mind....he was a bomb throwing caveman sort of fighter, as witnessed most ideally by his title winning bout vs Len Hutchins. and most of his fights in Argentina leading up to this fight. Victor relied on his immense strength and power in just bulldozing and overwhelming poor Hutchins...sending the guy to the hospital afterwards...and then transformed himself into a master counterpuncher....using counters, caution and strategy and thrived on winning 15 round decisions. His great countryman, Carlos Monzon, was also an adherent to a more patient, methodical ring style...which was more complementary to his master ring IQ and other skills, as arthritis, and a bullet in his arm took it's toll. Monzon was, IMO, the ultimate 15 round fighter, which this change of style necessitated. Emile Griffith...the grief he went through from the aftermath of the Benny Paret tragedy caused him to revert to the master mechanic, technical style he used throughout the rest of his career...also relying on winning 15 round decisions....and he was a master of going the 15 round route....he has more championship rounds than any other fight BTW. Dick Tiger also preferred going for points victories the older he got, despite the fact that he had immense strength and power. Humberto Gonzales....after that dramatic one punch ko loss to Michael Carbajal, reverted to a more patient, cagey fighter who preferred winning 12 round decisions. Tomorrow, when i think of more examples, I'll be back to this thread.
Barrera changed twice. When he started- and I followed him from his first US fight- he was a boxer. Watch his fights with Eddie Cook and Israel Perez. Later he became much more aggressive until reverting back to his original style.
Duran was an animal at lightweight. Then he lost to DeJesus, getting knocked down in the first round. And in the rematch he rushes in and gets knocked down again ... but this time comes back to win. Ray Arcel and Freddie Brown convinced him that if he fought the same way as always in the rubber match, DeJesus would be waiting for him with that left hook again. Thus was born a master boxer with finesse and controlled fury.
He didnt change style he changed sport, he became a wrestler! Hm I guess the initial change to brawler was for marketing purposes, many fighters have changed their styles a bit to be more fan friendly, once he became an established "star" and had also been beaten as a brawler he went back to what he did best, he already had the fans and nothing left to prove.
Edwin Rosario showed superb boxing skills early on but shelved them to a fair extent and became more of a hitter. Wilfredo Gomez did the same.
Vitali Klitschko hasn't been mentioned. His early upcoming fights was a guy with a nasty left hook that got guys out early. Not much with the right hand. > the rotator cuff surgery after the Byrdman, he lost that left hook and used it as a jab or hook as a range finder but no snap. Then, finished fights with the right hand. Later on when he was real old, he continued to win by throwing tons of combinations w/o much snap but getting by on volume. I think he and Galindez were the only champs to pretty much change everything and continue to defend the title.
Gomez lost those legs. He used to dip as low as anyone in the sport with the ability to fire out of it. Incredible how low he got. He was far more upright and lost those knee's long before the Sanchez bout. The amazing thing was all those successful title defenses he had after losing the legs. Usually a guy loses his legs in those lower weight classes, it's all over pretty quick.
I fail to see how that's different than Cotto, a boxer-puncher who bounced between styles according to what the game plan was against a specific opponent. Until DeJesus III, Duran had never shown that skill set before.