Vitali Klitschko punished Shannon Briggs for 12 brutal rounds Saturday to retain his WBC heavyweight title with a unanimous decision.
The Ukrainian champion dominated the action but never knocked down the American challenger.
"I am very surprised by how much he took," Klitschko said. "He's got a huge heart."
The judges scored it 120-107, 120-107 and 120-105 for Klitschko, who improved to 41-2. Briggs dropped to 51-6-1.
"I've fought George Foreman, I've fought Lennox Lewis, and Vitali's the best," Briggs said. "He hits harder than Foreman, he's got incredibly fast hands.
"This was my best fight."
Klitschko said Briggs deserved "a lot of respect."
"I could not believe he was still standing after taking so many punches," Klitschko said.
Klitschko used his left jab to set Briggs up for a big right two minutes into the opening round. Then two left hooks found Briggs' chin early in the second round and the Ukrainian landed some more rights, while Briggs unsuccessfully sought to hurt Klitschko with body blows.
Klitschko connected with several combinations in the third, but Briggs also found the target with counter-punches. The champion scored with a good right hook late in the round. He also finished the fourth strongly.
Briggs connected with a couple of good rights in the fifth, his best round, but also had to absorb several hard hits from Klitschko.
Klitschko continued to hit the American repeatedly with left-right combinations in the sixth, and Briggs took heavy punishment over the next few rounds but never went down.
The American was little more than a punching bag by the 10th, with Klitschko seemingly hitting him at will.
Briggs surprised Klitschko with a clean right in the 11th, but Klitschko replied with two big rights that snapped back Briggs' head. But the American only shook his head and stayed up.
Klitschko went for the knockout in the final round but Briggs withstood everything.