Ricky Hatton suffered a devastating second-round defeat in his IBO light-welterweight world title bout against Manny Pacquiao in Las Vegas.
Hatton, 30, was knocked down by a flashing right hook in the first round before being floored again by a left shortly before the bell.
Mancunian Hatton was pole-axed by a huge left in the second and counted out with one second remaining in the round.
The shattering defeat puts Hatton's future in the sport in doubt.
Hatton was defending his title but it was his second defeat in 47 fights, while Pacquiao now has 49 wins and three defeats from 54 fights.
I was just doing my job - Pacquiao
The victory confirmed Filipino Pacquiao's status as the number one pound-for-pound fighter in the world.
Hatton came into the fight at the MGM Grand Garden Arena as a big underdog, although few could have predicted the calamitous nature of the defeat.
Pacquiao, also 30, was fighting in his fourth weight division in as many fights, but his power was far too much for his rival, despite Hatton claiming beforehand that Pacquiao would be outmuscled.
The Filipino landed 73 blows to Hatton's 18, 65 of them power punches, while Hatton only landed with two jabs.
Pacquiao stunned Hatton midway through the first round with three straight rights before Hatton walked onto a right hook with a minute remaining.
Hatton rose on the count of eight but Pacquiao continued to pierce his leaky defence with lightning combinations before putting him down again with a booming left.
Hatton struggled to his feet but his legs had gone from beneath him and he was hanging on for dear life at the bell.
It was more of the same in the next round, with Pacquiao landing with two looping rights and a rapier left-right-left combination.
Referee Kenny Bayless warned Hatton for holding on the back of the head midway through the round, but Pacquaio was not perturbed, sending home a thunderous left hand that rendered Hatton unconscious before he had hit the floor.
There were some anxious moments as Hatton lolled on his back, but he eventually came round to hear only stunned silence from his thousands of fans.
He was taken to hospital for a precautionary brain scan.
Pacquiao, who started life as a flyweight, will no doubt fight the winner of the bout between Floyd Mayweather Jr and Juan Manuel Marquez on 18 July.
Hatton still has options, although it would not be a surprise if he decides to bring down the curtain on his stellar 12-year career as a professional.
Pacquiao's trainer Freddie Roach opened up the possibility of his man meeting the winner of Mayweather Jr and Marquez after Mayweather Jr announced on Saturday he was coming out of retirement.
"I think a fight with the winner of Mayweather-Marquez is a very good possibility," said Roach.
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