Errol Spence Jr lived up to his burgeoning reputation to maintain his undefeated record and win the IBF welterweight title, dethroning Kell Brook with an 11th-round stoppage in an enthralling contest at Bramall Lane.
With Brook's previous fight having come in a middleweight defeat to Gennady Golovkin, there had been concerns over the weight the Briton has had to lose to drop back down to welterweight.
It did not look as if those concerns would prove legitimate as Brook had the better of the early rounds in his home town of Sheffield, his size advantage playing into his hands.
But Spence grew into the fight and the American gradually began to dominate with a hugely impressive combination of quickness and power.
With Brook's left eye beginning to close he was dropped to one knee in the 10th and survived a standing count only to recover excellently and put Spence on the back foot towards the end of the round.
However, Brook could not see out the 11th, dropping to his knee again with his vision evidently impaired, the referee calling a halt to proceedings to hand Spence a 22nd successive victory.
Earlier, on the undercard, George Groves claimed his first world title at the fourth time of asking, a sixth-round stoppage of Fedor Chudinov seeing him win the vacant WBA super-middleweight belt.
Groves survived some early pressure from Chudinov but soon settled into his counter-punching rhythm and a sustained barrage to the head of the Russian prompted the referee to stop the fight, and a unification bout with IBF champion James DeGale could potentially be on the cards.