WBO welterweight champion Terence Crawford retained his WBO welterweight title after his fight with Amir Khan was stopped due to a technical knockout in the sixth round on Saturday night in New York. Khan had fallen behind early on, appearing to lose each of the opening three rounds after suffering a knockdown in the first. A promising start in which his speed troubled Crawford quickly became a struggle to survive after he was hurt by a right hand and then floored by a left. He appeared to have recovered by the end of the second, but despite occasionally landing is yet to enjoy periods of sustained success. Khan could no longer continue after a low blow, so he was ruled the loser via TKO after 47 seconds of the sixth. He had already begun to struggle with what appeared to be an injured right arm, and was taking regular punishment before he was withdrawn following Crawford's low blow. Khan said: "First of all I want to apologies to all of the fans. The fight was just getting interesting. Terence was great, I am not taking anything away from him. I have realised why he was one of the best pound for pound. I could feel that punch in the stomach and legs. I have never been hit below the belt and was in pain. "I could feel it in my stomach and legs. I said 'I can't move'. 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 will go and spend time with family and see where I go from there." Khan's trainer Virgil Hunter spoke up in defence of his fighter. He told the BBC: "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. "Amir didn't take the type of beating that says he should retire. He showed he could move – his legs aren't gone – but he fought a hell of a champion tonight. I will be honest with him when I think it's time to retire."