LAS VEGAS -- Rising welterweight Saul Alvarez stopped Jose Miguel Cotto with a rapid flurry of head shots late in the ninth round Saturday night to remain unbeaten.
Featherweight Daniel Ponce De Leon also earned a unanimous decision over Cornelius Lock on the undercard of Floyd Mayweather Jr.'s welterweight bout with Sugar Shane Mosley at the MGM Grand.
Alvarez (32-0-1, 24 KOs), a redheaded teenager from Guadalajara, Mexico, added to his growing reputation in his Las Vegas debut, rallying from a rough first round to outwork Cotto (31-2-1).
"It was just a matter of time," Alvarez said. "The first round was a little scary, but I gained my confidence as the rounds went on."
Cotto, the older brother of former champion welterweight Miguel Cotto, had Alvarez stunned on the ropes in the opening minutes. Alvarez shook it off and even sent Cotto stumbling to the canvas in the second round in a questionable knockdown.
Alvarez finally finished with a dominant ninth, repeatedly teeing off on Cotto's defenseless head until referee Tony Weeks stopped it with 9 seconds left.
"Fighting in Vegas was a great atmosphere," said Alvarez, who has won 28 straight fights since a draw when he was 15. "I want to come back and fight here again soon."
Cotto was stopped for the first time in his career.
Ponce De Leon's fifth straight victory had none of the usual theatrics for which the former 122-pound champion is known. The Mexican fighter gritted out a convincing victory over Lock, a 31-year-old Mayweather protege who has lost three of his last seven bouts.
"He was a very difficult fighter, but I did my best," Ponce De Leon said. "I won all the rounds at the beginning, so I stayed composed at the end. In the fourth round, I was cut by a head-butt, and it gave me some problems. Then in the eighth, I was hurt, but I kept my composure through that."
Earlier, welterweight Said Ouali stunned Argentina's Hector Saldivia with a first-round knockout. The bout was expected to be a showcase for Saldivia (31-2), who dropped Ouali in the opening moments -- but Ouali improbably rallied 40 seconds later for two knockdowns, capped by a right hook that stopped the fight.