Anthony Joshua lost his heavyweight world title belts to Andy Ruiz Jr in one of the biggest sporting upsets of all time, but he has vowed to get them back.

Joshua was a short as 1/25 to win on his American debut in Madison Square Garden, but Ruiz – who only took on the fight weeks before after the original opponent Jarrell Miller failed a drugs test.

The British ace is now focused on getting his IBF, WBA and WBO titles back, and he will have the chance later in the year as there was a rematch clause in the contract.

“Winning is everything. I am not going to sit here and say ‘losing is fine’. Not in my book. But if you do happen to lose, adjust and bounce back. But I do not condone losing in any form. This is war, battle, so what’s next?” said Joshua, who has had to put plans to take on Tyson Fury and Deontay Wilder on the back-burner.

“I still want to compete with those men but a rematch with Andy Ruiz Jr is where we are at,” he said. “I’m still a champ and I will rectify it to get the belts back.”

Joshua is odds-on to beat Ruiz in the rematch and is rated at 1/3 with leading bookmaker Coral.

The upset by Ruiz is being compared to Buster Douglas’ success against Mike Tyson in 1990 when Douglas was 40-1 in the betting to beat Tyson on that occasion.

“This is right up there with some of the biggest upsets in sporting history, according to the odds, with the obvious comparison being Buster Douglas’ surprise victory over Mike Tyson in 1990,” said Coral’s John Hill.

“AJ is the favourite avenge this defeat in the rematch, which is sure to take place later this year in the UK, however, the betting is much different this time around, with a lot more respect given to Ruiz Jr who will be defending his three belts,” added Hill.

Biggest upsets in betting history

40-1 Buster Douglas beating Mike Tyson in 1990

66-1 Japan beating South Africa in the 2015 Rugby World Cup

100-1 Horse Racing: Foinavon winning the 1967 Grand National