Muhammad Ali’s ‘Thrilla in Manila’ shorts expected to smash auction records

The shorts worn by Muhammad Ali during his famous “Thrilla in Manila” fight in 1975 are expected to smash auction records at Sotheby’s in New York next week.

The white satin Everlast trunks, which Ali signed with a black Sharpie pen, have attracted bids of $3.8m (£3m) in an online auction that closes on 12 April. That puts the trunks on course to become the most expensive item of Ali memorabilia sold at auction. Experts at Sotheby’s said they expected bids to increase to as much as $6m.

The bout against “Smokin’” Joe Frazier in 49C heat is widely regarded as one of the most brutal fights in the history of professional boxing. Ali, who described himself as “the greatest”, won the gruelling fight at the Smart Araneta Coliseum in the Philippine capital after the referee stopped the bout in the 14th round after 42 minutes. It was the third and final fight between the boxing legends. Ali beat Frazier 2-1 and retained his three heavyweight championship belts.

Related: The Thrilla in Manila - in pictures

The trunks, which are all white except for black trim at the waistband and black piping running down the side of each leg, are inscribed by Ali’s assistant trainer and corner man, Drew “Bundini” Brown, and signed by Ali in black Sharpie. The right leg inscription reads “Ali-Frazier Fight/Trilla in Manila” and the left leg reads “Pres F Marcos/Manila, Philippines/Oct 1 1975”.

Ali and Frazier’s first bout in 1971 was billed as the “Fight of the Century”, with Frazier emerging victorious after 15 rounds.

Ali was banned from the sport for three years because of his refusal to be drafted into the military during the Vietnam war.

In the lead-up to the Manila fight, Ali, who had nicknamed Frazier “the gorilla”, said: “It will be a killa and a thrilla and a chilla when I get the Gorilla in Manila”, while punching a gorilla doll. He explained that it was part of his pre-fight strategy: “I like to get a man mad because when a man’s mad, he wants ya so bad, he can’t think, so I like to get a man mad.”

Dave Wolf, a member of the Frazier team in Manila, said: “With all of the residue of anger that Joe had from what had happened before the first fight, what had happened before and during the second fight and after these fights, Joe was ready to lay his life on the line, and … he did.”

In the end, it was not Ali’s punches that brought about victory but Frazier’s inability to continue. With exhaustion taking its toll, Frazier’s corner decided to concede defeat by technical knockout.

The shorts are the lead lot in Sotheby’s sports week auction that also includes Michael Jordan’s game-worn Air Jordan 11s from the 1996 NBA finals. Two former Seattle Supersonics ballboys were each given one of the sneakers, which are expected to sell as a pair for $200,000-$400,000. There is also Kobe Bryant’s Los Angeles Lakers jersey from game 1 of the 2009 NBA finals, which is expected to fetch $1.5-$2.5m.

Ali was diagnosed with Parkinson’s in 1984 and died in 2016 aged 74.