Kell Brook requires surgery after breaking eye socket in defeat to Errol Spence Jr

Brook battled valiantly against Errol Spence Jr and more than matched his American foe for the large majority of the bout, but significant swelling around his left eye sustained in the seventh round took a severe toll.

He was knocked down in the 10th before taking a knee under no undue pressure in the following round, with referee Howard Foster calling a halt to proceedings at Bramall Lane.

The 31-year-old revealed on Sunday that he had sustained an identical injury to the one inflicted by middleweight king Gennady Golovkin eight months ago - albeit to the opposite eye broken by the Kazakh, nicknamed GGG.

Brook had a metal plate inserted into his face following the Golovkin defeat and is set to go under the surgeon's knife once more, while it seems unlikely he will box again this year.

"The eye is broken again, the same as the GGG one, I need surgery again and I am devastated. It kept going to double vision and that's why I went down on one knee," Brook said on Sky Sports News HQ.

Brook also admitted he had the words of his surgeon ringing in his ears following his fifth-round stoppage defeat to Golovkin in his last bout.

"I remember the surgeon telling me if I'd have gone a round or so extra (against Golovkin) I could have gone blind and I had that in my mind," he added.

His promoter Eddie Hearn acknowledged it will be another long road to recovery for Brook.

"It's a big blow to his career. There was a lot of pain going through the first one and now he's got to go through another one, but that's boxing," he said.

"It was caused by Errol Spence who is a great fighter and the better man won."

Spence Jr was rated "the real deal" by no lesser an authority than Sugar Ray Leonard and the 27-year-old lived up to the billing as his speed over Brook's power eventually told.

Brook was making the fourth defence of his world title but was fighting for the first time since suffering his maiden loss in the paid ranks when he stepped up two weight classes to challenge middleweight king Gennady Golovkin last September.

The 31-year-old sustained a broken right eye socket in the fifth-round stoppage loss which required surgery to repair and there were fears the injury, as well as coming back down to the 147lb division, could significantly hinder him, with even his promoter revealing he would have preferred his charge to campaign at light-middleweight.

But he opted to remain at welterweight and take on his mandatory challenger Spence Jr, who reached the quarter-finals at the London 2012 Olympics and came highly-rated from his fellow Americans, including Leonard and former pound-for-pound king Floyd Mayweather.

He did not seem remotely fazed by the occasion as he made the step up to world level for the first time after a successful first four years as a professional - despite being vociferously booed on his way to the ring.

The Texan landed a telling body blow early on but it was Brook who was enjoying the better of the exchanges in a largely cagey opening round before bringing the crowd to their feet with a flashy right hand and uppercut.

He was on the defensive in the next as Spence enjoyed his best round with more body blows although Brook did nail his foe with another crisp right hand.

Spence Jr, rated the favourite by bookmakers, was bleeding from his mouth at the start of the fourth but was starting to come into his own in a bout that was increasingly becoming a tactical battle.

The American was sent into the ropes and looked momentarily unsteady following an overhand right from Brook in the fifth, but the younger man came back strongly with a ferocious body attack that seemed to unsettle his opponent.

A couple of tight rounds ensued but Spence Jr's rapier punches seemed to be taking their toll as Brook's left eye started swelling rapidly.

Brook was left hanging on at the end of the ninth as the tide turned firmly in Spence Jr's favour, the challenger bombarding the champion with a flurry of blows.

Brook was down in the 10th after Spence Jr continued the assault but the Briton, roused by a boisterous home support, came roaring back and responded in kind.

But Brook, nursing the opposite eye that needed surgery, was down again, voluntarily taking a knee. It proved to be the final action as Spence Jr claimed a ninth stoppage win in a row and, most importantly, Brook's world title.

Brook said in the ring afterwards: "It was a very tough fight and he is one of the best I've been (in the ring) with, if not the best. I got caught in the seventh in the eye and it felt the same as against Golovkin.

"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."

Brook's promoter Eddie Hearn later revealed the 31-year-old had suffered the same type of injury to the opposite eye that he had sustained against Golovkin.

Hearn said: "He's gone to hospital, I think it's the same injury as the Golovkin fight but the other eye, which is unbelievable, but it was caused by Errol.

"No excuses about injuries or weight, he was beaten by the better man."