Joe Joyce (left) suffered a first career defeat and lost his WBO interim heavyweight titleBritish heavyweight Joe Joyce's world-title ambitions were derailed as he suffered a sixth-round technical knockout loss to China's Zhilei Zhang at London's Copper Box Arena.
Joyce, 37, was staggered several times and had no answer to Zhang's power as he suffered his first pro loss.
The ringside doctor twice inspected Joyce's swollen eye before the referee halted the contest in the sixth.
"I'm just disappointed with my performance," Joyce told BT Sport.
"The right hand he kept hitting me with... I couldn't get out of the way, so respect to Zhang.
"I expected to win like I normally do. Thanks for all the support and congratulations."
Joyce, the 2016 Olympic silver medallist, was the mandatory challenger for unified champion Oleksandr Usyk's WBO title and was on the cusp of a world-title shot.
He added: "I'm disappointed. I'd like to apologise to all my fans and supporters - I'll be back. My journey's not over, this is just a hurdle I've tripped over. I'll be back."
'Juggernaut' Joyce shocked by 'Big Bang'
Both Zhang (left) and Joyce are Olympic silver medallistsThis was not part of the script, with Joyce losing his WBO interim title.
Zhang - a 39-year-old, 6ft 6in southpaw with an accomplished amateur career - was far from a walkover opponent, but was the underdog.
Joyce entered the ring to the theme tune of sci-fi film Terminator, and it was a robotic performance from the Putney fighter.
He has been guilty of starting slow in the past, but even he looked surprised by the tremendous opening round from 'Big Bang', who hurt Joyce twice with big lefts.
'Juggernaut' Joyce has been commended in the past for having the best, and toughest, chin in the division, but he struggled to shrug off Zhang's heavy shots.
He became a sitting duck at times and was staggered by a left and then a huge right in the second before wobbling towards his own corner.
Blood began to pour from Joyce's nose, both eyes marked up and swollen.
Joyce was 1st 9lb lighter than his opponent at Friday's weigh-in, and Zhang's power could be heard from the thud of each punch to the Briton's temple.
Joyce desperately needed a response and started firing back in the fourth, but with his eye starting to close, there were concerns from his team the fight could be halted.
While the ringside doctor inspected Joyce between round five and six, Zhang smiled and acknowledged the crowd.
The fight was allowed to continue, but with Joyce's eyesight clearly hindered - and being repeatedly peppered by Zhang's punches - referee Howard Foster recalled the doctor in round six before deciding to save Joyce from any more, potentially long-lasting, damage.
'I will be back'
Zhang - who won silver at the 2008 Olympics - now boasts 25 wins, with 19 stoppages, one defeat and one draw.
"Today is mine," he said. "Today belongs to me, belongs to everyone who showed up, belongs to every Chinese fan who showed up."I'm 39 years old, but I'm disciplined, I train hard and next step I go for the title."
In fight week, Joyce said was targeting a world-title shot against Usyk, WBC champion Tyson Fury or a lucrative bout against Anthony Joshua.
He insisted he "will be back" and promoter George Warren said they may seek a rematch with Zhang.
Mayer impresses on undercard
Mikaela Mayer (right) has won 18 fights and lost once, a split-decision points defeat to compatriot Alycia Baumgardner in OctoberEarlier in the night, American Mikaela Mayer moved a step closer to a potential future showdown with Ireland's undisputed lightweight champion Katie Taylor as she beat late replacement Lucy Wildheart on points.
Former super-featherweight champion Mayer, 32, was the busier and more accurate boxer against the game Wildheart, who stepped in at 24 hours' notice after after Christina Linardatou failed a medical.
Sweden's Wildheart, 30, had the odd success early on but Mayer - who controlled the distance and got the better of the inside exchanges - dominated the middle and later rounds to win the vacant WBC interim title.
Mayer has her sights set on champion TaylorThe judges scored the fight 98-91, 98-92 and 100-90 to Mayer.
She said: "I do believe Katie Taylor and Amanda Serrano will go for their rematch. If that happens, I believe it will, I will challenge the winner.
"I feel great, I want the toughest fights possible. Right now that's Katie Taylor."
