Kell Brook gave a great effort, but in the end was overmatched in terms of power against middleweight king Gennady Golovkin, losing by fifth round stoppage when trainer Dominic Ingle threw in the towel during a Golovkin rally.

With the win, Golovkin improves to 36-0 (33 KO), and retains both the IBF and WBC middleweight titles. He also holds the WBA belt, which was not on the line in this fight. Brook falls to 35-1 (26 KO) with his first career loss, but is still the IBF welterweight titleholder.

The stoppage was questioned, but perhaps shouldn’t have been. When Ingle threw the towel in, Brook may not have been in any bell-ringing obvious danger, but he was getting worn out with body shots, and Golovkin was clearly hunting for something big in the round. Ingle was in the corner with Brook, who said after the fight that even though he felt he could fight on, he also couldn’t really see out of his right eye.

Previously in the fight, Brook had done some really good work, landing some uppercuts and other power shots, but after the fight Golovkin said he felt no power from his opponent. He did praise his ability, but said he’s not a middleweight.

Brook said after the fight that his right eye “had gone” a few rounds before the stoppage, and said he was “very dispirited,” that he had “much more to give.” “I believe I would have took over the middle to the last part of the fight,” Brook told HBO’s Jim Lampley.

Golovkin told Lampley that he wants to face WBO titleholder Billy Joe Saunders next, in order to unify all four middleweight title belts, which has long been his goal. The idea of a fight with Canelo Alvarez is still on hold until September 2017.