The boxing and mixed martial arts worlds are looking forward to the uneven match between undefeated American boxer Floyd Mayweather Jr. and MMA champ Conor McGregor. Although McGregor is confident he would knock out “Money May,” the loss of MMA fighters to boxers should be a lesson for athletes making a crossover of sports for the sake of the higher purse.

The best argument against MMA fighter fighting boxers in a boxing match is what happened to UFC fighter Tim Hague on Sunday. He died from injuries which Hague received from a knockout loss. Boxer Adam Braidwoods knocked out Hague in a boxing match on Friday night.

Multiple times KO

The bout, sanctioned by the Edmonton Combative Sports Commission, took place at the Shaw Conference Centre in Edmonton, Alberta, Canada.

Footage of the fight showed Braidwoods knocked down Hague several times. It was only when Braidwoods landed a brutal punch on his ring opponent and KOed Hague out cold did the referee stopped the bout, The New York Daily News reported.

Hague had a history of knockout losses. In his 34 MMA fights, he won 21 fights and lost 13 bouts of which eight were KOs. Four of the knockouts happened over the last two years. Hague, in July 2016, shifted to boxing after his last MMA match. He won only one match and lost three, two of which were knockouts.

McGregor is confident of a win vs. Mayweather

The so-called fantasy match between Mayweather and McGregor on August 25 at Las Vegas has attracted early bettors in favor of the UFC champ. McGregor is confident he would win his match against “Money May.” As part of his strategy to motivate himself, the UFC fighter had a massive mural made in his gym showing McGregor landing a punch on Mayweather’s face with his left hand, Fox Sports reported.

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South African boxer Chris van Heerden, who served as McGregor’s sparring partner for two matches, however, is wary the MMA fighter would win against Mayweather. He forecast Mayweather will beat Connor so badly, the organizers will stop the fight. The South African boxer, although he has an ax to grind against McGregor for not paying him and releasing footage of their sparring session even if he said he is against the idea, may be right.

Boxing, like MMA, is a brutal sport which often reduces even the best boxers to vegetables if they are knocked out badly. A day after Hague died, Argentinean boxer Saul Peralta is in a coma after a knockout loss, The Sun reported. It was his 15th fight on Saturday in Santa Fe when Peralta was KOed twice in the sixth round. His foe, Elias Arujo, has a 15-0 record, while Peralta is 9-5.