Russia's Artur Beterbiev knocked out British challenger Callum Johnson in the fourth round on Saturday to retain his International Boxing Federation light heavyweight world title.
Beterbiev, 33, maintained his perfect record with his 13th knockout win in 13 professional fights.
The 33-year-old Johnson, in his first world title fight, lost for the first time, falling to 17-1 but not before a game effort to topple the champion.
Beterbiev, who fights out of Canada, waded in early and dropped Johnson late in the first round.
The knockout artist was clearly looking to finish Johnson off in the second. He had landed a string of punishing blows when Johnson nailed him with a left hook that sent Beterbiev to the canvas at 1:24 of the second.
Beterbiev managed to stave off Johnson for the rest of the round, and the two traded more big blows in the third.
Beterbiev put Johnson down for the second time with 37 seconds left in the fourth, landing two rights to the challenger's head.
Johnson tried to rise, but he couldn't beat referee Celestino Ruiz's count before it reached 10 and it was over at 2:36 of the fourth.
“This is boxing. It’s one experience for me, my career. I’m happy. I’m happy for that fight. I win. I won by a KO. It’s good, I think so, no? Everyone can one time down, but it’s important if I win. I just remember he hit me not too strong. I remember that," Beterbiev said.
“I like to first see some proposals [for my next fight]. I’m happy to take a unified fight. I’m happy to again defend my belt, no problem. Everything. It’s my work. It’s my job.”
Johnson, who had fought just once in the past two years, admitted he was a bit "tense and nervous" coming in.
"Believe me, I'll be back, and I believe one day I'm going to be a world champion.".