MELBOURNE, Australia -- Novak Djokovic slammed Lance Armstrong's long-delayed doping admissions, saying the seven-time Tour de France winner is a disgrace to cycling and "should suffer for his lies."

At the same time, the No. 1-ranked man in tennis says the drug testing program in his sport is "good," though conceding that for the last six months he hasn't had a blood test in the anti-doping program.

"I think it's a disgrace for the sport to have an athlete like this," Djokovic, a lifelong cycling fan, said of Armstrong after his 6-4, 6-3, 7-5 win Friday over Radek Stepanek in the third round of the Australian Open. "It would be ridiculous for him to decline and refuse all the charges because it has been proven. He cheated many people around the world with his career, with his life story."

Maria Sharapova said after her 6-1, 6-3 win over Venus Williams that the Armstrong revelations are "just a really sad story, sad for that sport."

Said Serena Williams, "Unfortunately, I think a lot of people now look and are like, 'OK, if somebody is that great, what about everyone else in every other sport?' ''

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Victoria Azarenka added, "Everybody works so hard to be the best . . . You cannot go other ways."

After back-to-back 6-0, 6-0 wins in the first two rounds -- the first time that happened at a major since 1985 -- Sharapova has lost only four games en route to the fourth round at the Australian Open, matching Steffi Graf's record total through three rounds in 1989.

Third-seeded Serena Williams reached the fourth round with a 6-1, 6-3 victory over Ayumi Morita. The top-seeded Azarenka beat Jamie Hampton, 6-4, 4-6, 6-2.

Sam Querrey, the last remaining U.S. player in the men's draw, lost to 15th-seeded Stanislas Wawrinka, 7-6 (6) 7-5, 6-4.