Ruslan Chagaev won the WBA heavyweight boxing title from Nikolai Valuev with a majority decision on Saturday.
The taller and heavier Valuev lost the championship in his fourth defense since winning the belt 16 months ago.
The judges ruled for Chagaev 117-111 and 115-113, while the third called it 114-114.
Valuev's record dropped to 46-1 with a no decision, ending his bid to break Rocky Marciano's record of 49-0 without a defeat.
The Russian blamed the loss on his legs.
"Today I made a lot of mistakes and Ruslan was a few points ahead," Valuev said. "My biggest mistake was the stamina in my legs was not good."
Chagaev, the Uzbekistan fighter who calls himself "White Tyson," gave away 28cm and 44kg to the 2.13m Valuev.
But in the fourth round, he solved Valuev's jab, which had kept him at bay. After that, the fight turned into a slugfest, the kind Chagaev -- a fighter who throws a lot of punches -- wanted.
"For everybody who said Nikolai was too big and heavy for me, well its not important that I am smaller now, is it?" Chagaev said.
The 28-year-old, a former amateur world champion, ran his record to 23-0-1 with 17 knockouts.
Valuev won his previous title defenses outjabbing smaller opponents, but Chagaev lunged inside and caught Valuev with a left and short right to the temple in the fourth round and grew bolder.
He won the next three rounds the same way before 33-year-old Valuev hit him with several quick shots to take the eighth.
The pair stood toe-to-toe in the 12th, bringing the 6,800 spectators to their feet. Valuev took a hard left just before the bell.
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