Dmitry Bivol retained his WBA light-heavyweight world title and unbeaten professional record with a unanimous points decision over Saul "Canelo" Alvarez on Saturday.
The judges scoring handed the Mexican superstar just the second defeat of his career and the result comes as something of a surprise.
The 31-year-old Bivol improved to 20-0 with 11 knockouts while multiweight champion Alvarez, slips to 57-2 with two draws also on his record.
The only other defeat suffered by Alvarez came against Floyd Mayweather at light-middleweight in 2013.
Alvarez made history back in November after he stopped Caleb Plant to unite all four super middleweight world title belts, a unique feat in the world of boxing.
He had been confident of making the step up, but struggled with the power of his opponent.
Dmitry Bivol plays spoiler against Canelo Alvarez
The loss to Bivol was not his first at light-heavyweight before, with Alvarez stopping Sergey Kovalev in the 11th round to win the WBO title in November 2019.
Bivol guarded well and the only injuries he had to show for his encounter with Alvarez were a few bruises on his arms.
"He hurt my arm," Bivol said after the fight.
"I felt his power, you can see on my arm. He beat my arm up -- but not my head."
All three judges scored the bout 115-113 for Bivol.
The largely pro-Alvarez crowd packed into the T-Mobile Arena in Las Vegas left deflated as their man was unable to mount any significant offence and Bivol said the crowd helped fire him up.
Bivol insisted that the partisan cheers for Alvarez gave him more energy.
Sucking the air out of the room
Bivol kept a cool head and fought a disciplined fight, building his attacks around a forceful jab that would help him open the door for powerful combinations that kept Alvarez off-balance.
With Bivol constantly coming forward, Alvarez was thrown back, and couldn't manufacture a response.
By the time the seventh round rolled around, Alvarez's face was heavily bruised, while his feet grew heavy and his punches didn't have enough behind them to impact Bivol.
"He's a very good fighter," Alvarez said. "He comes in, goes out. He managed his distance really well. That's boxing.
"He's a great champion," Alvarez said. "I lost. He won."
Although he had no complaint with the decision, Alvarez did insist that he wanted a rematch.
"Rematch? No problem," Bivol said. "Let's talk about that."