LONDON (AP) " Jumping two weight classes to challenge Gennady Golovkin, Kell Brook's ambitious challenge wasn't given much hope.
Despite that leap, a valiant Brook made it far tougher for the world middleweight champion than anticipated as they traded punches for four rounds in a thrilling, open contest Saturday night in London.
But Brook's vision was affected after his right eye socket was broken in the second round and the previously unbeaten welterweight champion began to fade. After the formidable Golovkin unloaded a rapid succession of powerful punches in the fifth round, the Brook's corner threw in the towel.
"The last round he couldn't breathe or move," Golovkin said.
The 30-year-old Brook was taken to a hospital from O2 Arena in London for his eye to be assessed.
"I am gutted because there was much, much more to come from me," Brook said before leaving the ring. "I was just getting started but I was seeing five of them out there, I think I have bust an eye socket."
The 34-year-old Golovkin was full of praise for Brook but never felt his WBA, WBC and IBF middleweight belts were under threat.
"I know my style, I respect him, he's good but not so strong," Brook said. "He just touched but I didn't feel his power. So many punches but I didn't feel them."
The Kazakh improved his record to 36-0 and is now targeting a unification fight with Billy Joe Saunders to claim the minor WBO title.
"I'm open for everybody," Golovkin said.
Brook succumbed to the first defeat of his professional career in his 37th fight after being one of the few fighters willing to take on the fearsome Golovkin. After initially looking unsteady and anxious, Brook grew in confidence landing left hooks on Golovkin and unsettling him with three-punch combinations in the second round.
"I expected him to be a bigger puncher," Brook said. "In the second round he broke my eye socket but I was tricking him, I was frustrating him. I was starting to settle into it but when you see three, four, five of them it's difficult.
"I hurt him. When you're in the fight you can see, his legs buckled a little .... I would fight him again, with a good eye."
Brook's trainer, Dominic Ingle, was jeered by the capacity arena crowd after throwing in the towel. But the swelling on a cut by Brook's right eye showed he couldn't continue. He was tiring as a resilient Golovkin was showing he could not be worn down.
"You can't be fighting a guy like Golovkin when you can't even focus on the guy," promote Eddie Hearn said, referring to Brook's eye injury.
This story has been automatically published from the Associated Press wire which uses US spellings