Filip Hrgovic of Croatia beat Britain's Moses Itauma via a ninth-round stoppage to win the vacant IBF world heavyweight title in a thrilling contest at London's O2 Arena on Saturday.
Itauma, bidding to become the second-youngest heavyweight world champion after Mike Tyson, was on top during the fight's early stages but had to be carried from the ring on a stretcher and taken to hospital.
Facing the toughest test of his 15-fight professional career against an experienced Olympic medal winner, the 21-year-old Itauma tired against an opponent with a granite chin.
Itauma's trainer Ben Davison threw in the towel in the ninth round, but by that time referee Howard Foster had stopped the fight in Hrgovic's favour as the Croat won the International Boxing Federation version of the world heavyweight title vacated by Oleksandr Usyk.
It was Itauma's first time beyond the sixth round, and at one point in the ninth he looked as if he was about to topple.
"I don't know from where I got energy in that (ninth) round," said the 34-year-old Hrgovic, almost as spent physically as his beaten opponent.
"It was really not my strength. It was Holy Spirit. He gave me strength in this camp to endure everything, to have (the) best camp of my life, he put me in touch with this great coach Abel Sanchez."
Hrgovic saluted the courageous Itauma by adding: "I'm the present, and he's definitely (the) future. He's an amazing fighter. He's one of a kind. He's the best I've been in a ring with, but he needed more experience.
"I felt the pace of the fight. I knew I was losing rounds, but I knew that I had that pace in my favour. He was gassing out."
Itauma landed with several straight left hands early on and Hrgovic was given a standing eight count in the second after being caught with a right hook.
Itauma's uppercut at the end of the fifth round had home fans in a partisan crowd standing in appreciation.
But come the eighth, both boxers appeared out on their feet, with Hrgovic somehow still standing despite several punishing blows.
Hrgovic was landing powerful shots of his own and, with a dazed Itauma lurching around the ring, Foster called a halt in the ninth round.