This is the accidental punch that brought about the end of the fight for Amir Khan.
Sorry there weren't a few more rounds to enjoy, but that's the way it goes sometimes.
Two big questions now: What next for Amir Khan? And how good is Terence Crawford?
These will be debated on the Costello & Bunce podcast available later today, and there will be further reaction on the BBC Sport website's boxing index.
Thanks for joining us, and enjoy the rest of your day.
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Post update
Steve Bunce
BBC Radio 5 live boxing pundit at Madison Square Garden
Khan has fought almost half his life under the lights. He's given us a decent highlights reel. You can take his career and there will be better fighters but he holds his own, maybe not in the top five, but in the top 25 British fighters of all time.
'Crawford greatly impressive'
Steve Bunce
BBC Radio 5 live boxing pundit at Madison Square Garden
I saw a different Crawford tonight. He was so comfortable at any distance and he can fight with any stance he wants to. I was greatly impressed.
What next for Khan?
Steve Bunce
BBC Radio 5 live boxing pundit at Madison Square Garden
Amir will fight on if there's something big on the table. If for some reason Matchroom can make that Brook fight generate £4m or £5m he'll fight. But he will not fight people for peanuts, he'll end up in big-money fights.
Post update
Steve Bunce
BBC Radio 5 live boxing pundit at Madison Square Garden
It was a fight of several fights. There was the cool, calm, calculating Crawford, there was the Amir looking tense, the Amir caught and dropped in the first round, the Amir who just got through some other rounds and then the Amir who was trying to land punches.
Amir struggled with his right elbow but 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.
We said before the fight that he will lose but he will go down swinging. And if ever there was a fighter who did that it was Amir Khan.
Post update
Trainer Virgil Hunter on Radio 5 Live: "The crowd will always be blood thirsty 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.
"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."
Just tuning in...
Crawford beats Khan
Getty ImagesCopyright: Getty Images
If you are just joining us.
- Amir Khan was floored in round one
- Terence Crawford controlled the five rounds to follow
- In the sixth round, a low blow from Terence Crawford caught Khan in the groin
- Khan went to his corner and was entitled to five minutes recover. He did not take the time and instead the fight was ended
- Khan says he told his corner he could not continue because the "pain was too much"
- Crawford retains his title with a TKO win
Crawford so good
Paulie Malignaggi
Former welterweight world champion on BBC Radio 5 Live
When you can make guys miss punches even by millimetres that means he's in the perfect position for a power counter and Crawford does that so well.
From close up here I can really appreciate his skills.
Post update
The judges had it 49-45 50-44 49-45 in favour of Terence Crawford at the time of the bizarre ending.
Crawford wants Spence...
Crawford beats Khan
WBO welterweight champion Terence Crawford: "There's only one fight they talk about and that's Errol Spence. Whenever he's ready I'm here.
"I can't put a gun to a promoter's head and make them make the fight. All I can do is fight everyone in front of me and we make it happen sooner or later."
Post update
Paulie Malignaggi
Former welterweight world champion on BBC Radio 5 Live
It was anti-climatic for sure but Amir has had a long career and a lot of big fights and you don't want to see someone who has had a great career take punishment.
He may get criticism but I can't fault him because he's had so many tough fights and he deserves a break.
'Too much pain'
Crawford beats Khan
Amir Khan speaks to BT Sport: "The fight was going well. I was getting caught but catching him with some. I got hit with a shot beside my cup. The pain went down my legs.
"Virgil asked me how I feel, I couldn't continue as the pain was too much.
"I have had some problems in my right arm. I'm not complaining about it but was getting some sharp pain. He caught me with a great shot early in the fight.
"I knew the mistake I made. I was trying too hard.
"He's better than I thought. He's quick, sharp, a great fighter.
"I want to apologise to everybody. I tried."
'Took his moment'
Crawford beats Khan
Paulie Malignaggi
Former welterweight world champion on BBC Radio 5 Live
I think Khan just needed a moment to be done. That was his moment.
More from Amir Khan on the low blow: "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".
'A storm to come'
Mike Costello
BBC Sport boxing correspondent at Madison Square Garden
If the reaction of the crowd is anything to go by Amir Khan could be in for a storm of abuse.
Amir Khan reaction...
Amir Khan speaks in the ring: "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."
'Best way for fight to end for Khan'
Paulie Malignaggi
Former welterweight world champion on BBC Radio 5 Live
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.
Post update
That was ugly.
Ugly in many ways. The knock down, the one-way traffic, the punch in a sensitive area, and, the conclusion.
Crawford wins by technical knockout
Khan v Crawford
The blue corner tell the referee their fighter can't continue.
"The winner by technical knockout, still the WBO welterweight champion of the world.... Terence Bud Crawford".
Live Reporting
Luke Reddy
All times stated are UK
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Latest PostCrawford beats Khan after low blow
This is the accidental punch that brought about the end of the fight for Amir Khan.
Sorry there weren't a few more rounds to enjoy, but that's the way it goes sometimes.
Two big questions now: What next for Amir Khan? And how good is Terence Crawford?
These will be debated on the Costello & Bunce podcast available later today, and there will be further reaction on the BBC Sport website's boxing index.
Thanks for joining us, and enjoy the rest of your day.
Post update
Steve Bunce
BBC Radio 5 live boxing pundit at Madison Square Garden
Khan has fought almost half his life under the lights. He's given us a decent highlights reel. You can take his career and there will be better fighters but he holds his own, maybe not in the top five, but in the top 25 British fighters of all time.
'Crawford greatly impressive'
Steve Bunce
BBC Radio 5 live boxing pundit at Madison Square Garden
I saw a different Crawford tonight. He was so comfortable at any distance and he can fight with any stance he wants to. I was greatly impressed.
What next for Khan?
Steve Bunce
BBC Radio 5 live boxing pundit at Madison Square Garden
Amir will fight on if there's something big on the table. If for some reason Matchroom can make that Brook fight generate £4m or £5m he'll fight. But he will not fight people for peanuts, he'll end up in big-money fights.
Post update
Steve Bunce
BBC Radio 5 live boxing pundit at Madison Square Garden
It was a fight of several fights. There was the cool, calm, calculating Crawford, there was the Amir looking tense, the Amir caught and dropped in the first round, the Amir who just got through some other rounds and then the Amir who was trying to land punches.
Amir struggled with his right elbow but 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.
We said before the fight that he will lose but he will go down swinging. And if ever there was a fighter who did that it was Amir Khan.
Post update
Trainer Virgil Hunter on Radio 5 Live: "The crowd will always be blood thirsty 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.
"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."
Just tuning in...
Crawford beats Khan
If you are just joining us.
- Amir Khan was floored in round one
- Terence Crawford controlled the five rounds to follow
- In the sixth round, a low blow from Terence Crawford caught Khan in the groin
- Khan went to his corner and was entitled to five minutes recover. He did not take the time and instead the fight was ended
- Khan says he told his corner he could not continue because the "pain was too much"
- Crawford retains his title with a TKO win
Crawford so good
Paulie Malignaggi
Former welterweight world champion on BBC Radio 5 Live
When you can make guys miss punches even by millimetres that means he's in the perfect position for a power counter and Crawford does that so well.
From close up here I can really appreciate his skills.
Post update
The judges had it 49-45 50-44 49-45 in favour of Terence Crawford at the time of the bizarre ending.
Crawford wants Spence...
Crawford beats Khan
WBO welterweight champion Terence Crawford: "There's only one fight they talk about and that's Errol Spence. Whenever he's ready I'm here.
"I can't put a gun to a promoter's head and make them make the fight. All I can do is fight everyone in front of me and we make it happen sooner or later."
Post update
Paulie Malignaggi
Former welterweight world champion on BBC Radio 5 Live
It was anti-climatic for sure but Amir has had a long career and a lot of big fights and you don't want to see someone who has had a great career take punishment.
He may get criticism but I can't fault him because he's had so many tough fights and he deserves a break.
'Too much pain'
Crawford beats Khan
Amir Khan speaks to BT Sport: "The fight was going well. I was getting caught but catching him with some. I got hit with a shot beside my cup. The pain went down my legs.
"Virgil asked me how I feel, I couldn't continue as the pain was too much.
"I have had some problems in my right arm. I'm not complaining about it but was getting some sharp pain. He caught me with a great shot early in the fight.
"I knew the mistake I made. I was trying too hard.
"He's better than I thought. He's quick, sharp, a great fighter.
"I want to apologise to everybody. I tried."
'Took his moment'
Crawford beats Khan
Paulie Malignaggi
Former welterweight world champion on BBC Radio 5 Live
I think Khan just needed a moment to be done. That was his moment.
Post update
Boxing journalist Ron Lewis...
'I am not one to give up'
Crawford beats Khan
More from Amir Khan on the low blow: "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".
'A storm to come'
Mike Costello
BBC Sport boxing correspondent at Madison Square Garden
If the reaction of the crowd is anything to go by Amir Khan could be in for a storm of abuse.
Amir Khan reaction...
Amir Khan speaks in the ring: "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."
'Best way for fight to end for Khan'
Paulie Malignaggi
Former welterweight world champion on BBC Radio 5 Live
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.
Post update
That was ugly.
Ugly in many ways. The knock down, the one-way traffic, the punch in a sensitive area, and, the conclusion.
Crawford wins by technical knockout
Khan v Crawford
The blue corner tell the referee their fighter can't continue.
"The winner by technical knockout, still the WBO welterweight champion of the world.... Terence Bud Crawford".