Timothy Bradley survived a late knockdown to defend his WBO welterweight title with a unanimous decision over Ruslan Provodnikov in Carson, California.
The American took the verdict by margins of 115-112 and 114-113 (twice) to stretch his unbeaten record to 30-0.
But it was one of his toughest nights as the big-punching Provodnikov dominated the early stages of what turned out to be 12 rounds of non-stop action.
Bradley was fortunate that referee Pat Russell ruled it a slip when he went down in the opening round and he appeared wobbly and on the brink of defeat as the second drew to a close.
But the champion found his legs in the third and picked off the come-forward Provodnikov at will during the middle rounds, causing huge cuts and swelling on the Russian's face.
Provodnikov rallied late on and one last barrage sent Bradley to the canvas with 10 seconds remaining in the 12th round. He was able to quickly regain composure and took a knee before the final bell came to his rescue.
"I gave it everything I had. Every ounce I had, I gave," said Bradley, who was fighting for the first time since beating Manny Pacquiao on a split decision last June.
"He's much more powerful than Pacquiao. He hits harder, and has shorter punches. He's a great puncher, and I take my hat off to him."
Provodnikov, whose career record drops to 22-2, felt he had done enough to sway the judges.
"I was the clear winner," he said through a translator. "I hurt him. I knocked him down. I don't know what else to do."
Do you agree with the judges?
Yes - Timothy Bradley was a deserving winner
No - Ruslan Provodnikov did enough to get the verdict
Draw - It was too close to call