Amir Khan’s shot at WBO world welterweight champion Terence Crawford ended in bizarre fashion when a low blow saw him pulled out by his corner.
Khan, floored in the opening round, took an accidental shot to his groin in the sixth and after consulting his corner said he was in “too much” pain.
Crawford dominated the contest and later questioned whether Khan quit, urging the Briton to “tell the truth”.
“I would never quit, I would rather get knocked out,” Khan said.
“I have never been hit below the belt and was in pain.
“I want to apologise to all of the fans. The fight was just getting interesting.”
Boos rang out at New York’s Madison Square Garden upon the conclusion, prompting BBC Sport commentator Mike Costello to say Khan “could be in for a storm of abuse”.
Former world middleweight champion Andy Lee said Khan had “done himself a mis-service”, while former two-weight world champion Paulie Malignaggi said the Briton “wasn’t going to get back into the fight”.
‘I could not continue’
Khan, a heavy underdog against an undefeated American who has held world titles in three weight divisions, looked nervy during his ring walk and a right hand saw him stagger in round one, allowing Crawford to send him to the canvas.
He was unable to live with the slickness the champion brought and took hard shots to the body in round four, landing sporadic – if light – punches of his own.
When Crawford drove a left hook into his groin in the sixth, Khan was legally allowed to take five minutes to recover but after around a minute, the bell sounded.
“I could feel it in my stomach and legs. I said ‘I can’t move’,” Khan added. “There was no point taking five minutes out, I could not continue. I am not one to give up. I was hit by a hard shot below the belt.
“I couldn’t continue as the pain was too much.”
When an accidental injury ends a bout in which four rounds have been contested, the judges’ cards are used but the announcement of a technical knockout meant Khan – after consulting his corner – was stopped.
Boos were audible but Crawford appeared relaxed at the sound of the bell, despite general confusion as to whether he risked disqualification.
The champion led 49-45 50-44 49-45 on the cards at the time and immediately said he hoped to face IBF champion Errol Spence Jr next.
‘Did you quit? Tell the truth’
British rival Kell Brook told reporters he thought Khan “quit”.
And in the post-fight news conference Khan was responding to claims he had done when Crawford interrupted, stating: “Did you quit? Tell the truth”.
Malignaggi added: “That’s probably the best way for Amir to leave the ring because it means he’s not going to take any more punishment. He wasn’t going to get back into the fight.
“I think Khan just needed a moment to be done. That was his moment.”
Khan’s trainer Virgil Hunter told BBC Radio 5 Live: “The crowd will always be bloodthirsty and want to see a dramatic ending but you have to look out for the safety of the fighter. He’s not the kind of fighter to make things up. I believe he was incapacitated.
“We knew we were behind but Amir was starting to work things out and pick up his rhythm.”
BBC Radio 5 live analyst Steve Bunce said Khan had been struggling with an elbow injury, adding: “All he kept saying in the ring was how sorry he was for letting people down.
“I’ve seen fighters in small halls getting thrown out for shots like that, accidental or intentional.”
More to follow.