Kell Brook was stopped by Errol Spence Jr in the 11th round after suffering a nasty injury at Sheffield's Bramall Lane.
With his eye badly swollen, Brook couldn’t take any more and dropped onto one knee with referee Howard Foster calling a stop to the fight.
It meant Spence Jr became the new IBF welterweight champion after what was an incredible battle.
Unfortunately for Brook, it’s an all too familiar story for him. He suffered a similar eye injury - albeit the other one - in the loss to Gennady Golovkin last September.
During that loss last year, he broke an orbital bone and there will be immediate fears that he has done the same against Spence.
Spence was ahead on all three judges’ scorecards at the time of the stoppage and was heading for a points victory before Brook dropped to his knees.
Watch: The moment Brook quit
Take a look at the moment Brook simply couldn’t take any more:
Brook had previously been against the ropes in the previous round - round 10 - but somewhere survived a Spence onslaught.
Afterward, Brook explained why he simply had no alternative but to give up.
Brook explains why he quit
"It was a very tough fight and he is one of the best I've been with, if not the best. I got caught in the seventh in the eye and it felt the same as against Golovkin (when Brook fractured his eye socket),” he said.
"I couldn't see out of the eye, so I had to stop. I thought it was very competitive, he won a few rounds, I won a few rounds, I felt I was in the fight. I'm gutted, devastated that in front of my own fans I've lost my belt."
Hearn suggests Brook's next move
Brook’s promoter, Eddie Hearn, also spoke following his loss and suggested that his fighter should move to light-middleweight, with a possible fight against Amir Khan on the cards.
"He took this fight because he didn't want to vacate (his title),” Hearn said.
"He broke his eye socket in the seventh round and kept going.
"Kell is stubborn, I believe he should move to light-middleweight. Amir Khan is a fight we have wanted for five years, but at the moment it is all about making sure Kell is OK."
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