Pacquiao, who became the first boxer to win seven championships in as many weight classes, underwent urine tests twice -- before and after the fight -- and both came back negative, said Keith Kizer, executive director of the Nevada State Athletic Commission. It's the the 10th time the Filipino has turned in clean tests in Nevada.
Immediately following his win over Cotto, fans inside the MGM Grand Arena pleaded for a megafight with Floyd Mayweather Jr., who many have regarded as the top pound-for-pound fighter since his return in September. In response to the expected fanfare, Floyd Mayweather Sr. publicly accused Pacquiao of taking steroids.
Mayweather Sr., Floyd's father and trainer, told SI's Chris Mannix that he believed Pacquiao's ability to take Cotto's powerful shots and keep coming proved the champion was taking performance-enhancing substances. "I know Floyd is the best," said Mayweather Sr. "But when [your opponent] uses something illegal, even the best can get hurt."
Floyd Sr. offered no evidence to support his claim.
Since 2002, Nevada has required fighters to submit urine samples before every fight. Those samples test for 40 types of steroids, diuretics and masking agents. In his 10 Las Vegas fights, Pacquiao has never tested positive, and his conditioning coach, Alex Ariza, said the only substances his fighter took leading up to the fight with Cotto were whey protein and liver-support supplements, in addition to his 6,500-calorie diet.
Pacquiao has been bombarded with accusations of doping, having conquered seven weight divisions since entering the sport at 106 pounds when he was 16. And after Mayweather Sr.'s comments following the Nov. 14 bout, there has been speculation that if a megafight between Floyd Jr. and Pacquiao is agreed upon, Mayweather's camp may place stipulations in the fight contract that would require both fighters to take separate, mandatory drug tests in addition to the required tests by state athletic commissions.
But at 10-0 with his Nevada drug tests, Pacquiao has provided plenty of proof he cleanly fought his way to seven world titles.