Vladimir Klitschko of Ukraine retained the International Boxing Federation heavyweight world title on Saturday when he stopped previously unbeaten challenger Calvin Brock in the seventh round at Madison Square Garden.
Brock crumpled to the canvas after taking a devastating right-hand punch to the jaw. The American rose to his feet after the count but was so wobbly that referee Wayne Kelly waved an end to the scheduled 12-round bout at 2:10 of the seventh.
"It was a left hook, straight right combination," Klitschko told reporters. "I should have landed it that way earlier in the fight. But it took that much time to get my rhythm and distance. He's a good defensive fighter."
Klitschko, 30, improved to 47-3 with 42 of his wins coming within the distance.
The 31-year-old Brock, a member of the 2000 US Olympic boxing team, suffered his first defeat after winning his opening 29 professional bouts.
"I saw the punch coming but I couldn't react fast enough," Brock said. "He's strong."
Earlier, Muhammad Ali was lavished with cheers of "Ali, Ali, Ali," when he arrived to take a front row seat for his daughter Laila Ali's defence of her super middleweight title against fellow-American Shelley Burton.
The 28-year-old WBC women's champion unleashed a powerful left-right combination that busted Burton's nose in the fourth round. With blood pouring from the challenger's face, the referee stopped the bout and Ali improved her record to 23-0.