Amir Khan was beaten by WBO world welterweight champion Terence Crawford in controversial circumstances at Madison Square Garden.
Having been floored in the opening round, Khan received a low blow to his groin in the sixth and pulled out of the fight after saying he was in “too much” pain.
Crawford was the superior boxer and he later questioned whether Khan quit, which the Briton denied.
“I would never quit, I would rather get knocked out," Khan said, per BBC Sport.
"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."
The MSG was filled with boos upon the conclusion of the main event.
Khan's controversial defeat
Khan was simply unable to cope with Crawford’s class but many boxing fans will feel as though he simply quit.
Khan knocked down in round one
Khan 'quits' after low blow in round six
The 32-year-old was permitted five minutes to recover after being hit in the groin in the six, but the bell sounded after around a minute.
"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."
Crawford was awarded the win via TKO, taking his record to 35-0.
The American was ahead 49-45, 50-44, 49-45 on the judges’ cards at the time of the stoppage.
Crawford said after the fight that he wants to face IBF champion Errol Spence Jr. next.
As for Khan, his boxing career could be over.
A fight against rival Kell Brook has been speculated for some time and Brook believes that’s the only option for the Bolton-born fighter now.
“I thought he quit. He had five minutes. He just looked for a way out, he were getting beat in every department,” Brook told AB Boxing News.
“He will wanna fight me now, he’s got nowhere to go,” Brook told AB Boxing News.News Now - Sport News