Hagler’s official website later said that the American had died of natural causes and was a “champion until the end”.
One of the most popular, talented and durable figures from a truly golden era for boxing, Hagler reigned supreme as the undisputed middleweight champion of the world between 1980-87 after dominating Britain’s Alan Minter at Wembley Arena.
His battles with the likes of Roberto Duran and Thomas Hearns have gone down in the sport’s folklore, with the first round of his epic war with “The Hitman” at Caesars Palace in Las Vegas in 1985 arguably the most enthralling ever seen in a boxing ring.
Footage of that classic bout – widely ranked as among the best of all time despite only lasting for three rounds – has been shared across social media since news of Hagler’s passing, with Hearns recently telling the Associated Press: “I can’t take anything away from him.
“His awkwardness messed me up but I can’t take anything away from him. He fought his heart out and we put on a great show for all time.”
Only a controversial split-decision defeat against fellow middleweight great Sugar Ray Leonard in another high-profile contest known as ‘The Showdown’ in 1987 led to the end of Hagler’s historic reign.
That was to prove his final fight before he called time on an illustrious career that began in 1973 and saw him claim 62 wins and 52 knockouts from 67 total fights, with two draws and only three losses.
Leonard told Sports Illustrated’s Chris Mannix on Saturday that the bruising clash – the result of which is still hotly disputed to this day – was the “closest I’ve been to death”.
There was a poignant 10-bell tribute to Hagler – who legally changed his name to Marvelous Marvin in 1982 – led by legendary announcer Michael Buffer at Dazn’s show in Dallas on Saturday night, while former heavyweight champion and close friend Larry Holmes wrote on social media: “The boxing world is sad to hear the news about Marvin Marvelous Hagler.
“A tragedy happened today, one of my best friends passed away. He was a good guy, a good man. May his soul RIP.”
Trainer Teddy Atlas said on Twitter: “He was a no frills solid man, who brought a lunch pale filled with power, guts, pride, will, talent and character. And he fought everyone, anytime, anywhere. And he was great. He was Marvin Hagler. R. I. P. Champ.”
Oscar De La Hoya said: “Saddened to hear about the death of Marvelous Marvin Hagler. One of the greatest to ever step in the ring! #RIPMarvelous.”
Promoter Frank Warren’s tribute read: “Rest In Peace Marvelous Marvin Hagler. Boxing lost an all time great today.”
British heavyweight Dereck Chisora also hailed Hagler as “one of the greatest to ever do it.”
Barry McGuigan wrote: “Shocked and deeply saddened to hear of the passing of the incredible Marvellous Marvin Hagler. I’m honoured to have spent some amazing times with him.
“My heartfelt sympathies to his wife Kay and his family. Rest in Peace Champ.”
Nicola Adams said: “Rip Marvin Hagler, what a fighter he was. #Champ.”
Freddie Roach wrote: “Marvin Hagler came to my fight in Boston. I appreciated what he said to me after my fight. Rest In Peace, my friend. Condolences to the Hagler family. Thank you Marvelous Marvin Hagler for all you gave to boxing.”
“Marvelous Marvin Hagler was an undisputed champion in the ring, and a wonderful friend and ambassador for the positive power of sport out of it,” said Laureus World Sport chairman Sean Fitzpatrick.
“The thoughts of the entire Laureus Academy are with Marvin’s wife, Kay, his family, and loved ones. Rest in peace.”
Heavyweight legend Lennox Lewis wrote of his friend: “I’m simply stunned to hear the news of Marvelous Marvin Hagler. Not only was he a living legend, but I was proud to call him my friend. He was so full of life, energy and positivity in our conversations that you would never guess what a wrecking machine he was in the ring.
“Our wives would speak on the phone to connect us and I’ll miss his voice saying “It’s Marvelous” on the other end of the line. We were anxiously looking forward to seeing him at our League of Champions Boxing Camp when it reopened.
“This one hits so hard also because he was the one I emulated my own training camps after when I saw how seriously he took his training camps. The world is one great man less today.
“From my family to Kay, and the entire Hagler family, our deepest sympathies go out to you and we’re sending prayers for strength & guidance.”
Top Rank chief Bob Arum said: “Marvelous Marvin Hagler was among the greatest athletes that Top Rank ever promoted.
“He was a man of honor and a man of his word, and he performed in the ring with unparalleled determination. He was a true athlete and a true man. I will miss him greatly.”