MELBOURNE, Australia (AP) — Novak Djokovic absorbed plenty of pressure from Radek Stepanek before advancing to the fourth round of the Australian Open, then unleashed some stinging shots at Lance Armstrong after the doping-tainted cyclist’s long-expected confession.

Djokovic broke the 34-year-old, 34th-ranked Stepanek late in each set of a 6 -4, 6-3, 7-5 win yesterday, extending his winning streak to 17 matches at the Australian Open.

In the next match on Rod Laver Arena, Maria Sharapova beat Venus Williams 6-1, 6-3 in an unexpectedly lopsided third-round result.

Williams could consider herself fortunate — Sharapova’s opponents in her first two matches failed to win a game from the Russian star.

Three matches into this tournament, and Sharapova, who pumped her arms six or seven times after she served out with an ace, has lost just four games heading into her fourth-round match against unseeded Belgian Kirsten Flipkens.

“I think when we both looked at the draw, it was a matchup we were both looking forward to,” Sharapova said of Williams, a seven-time major winner. “I was a really determined player out there because I knew the tennis that she’s capable of producing and playing. She’s a tremendous athlete and a great champion.”

Williams didn’t feel like a great player on Friday.

“Definitely not my best today, but there’s always other days to play better,” she said. “I just had a lot of errors (26) … that never helps.”

At Djokovic’s post-match news conference, the questions quickly turned from tennis to Armstrong’s confessions about doping in cycling during his television interview with Oprah Winfrey in the US Thursday night.

“I think it’s a disgrace for the sport to have an athlete like this,” said Djokovic, the number one-ranked man in tennis. “He cheated the sport. He cheated many people around the world with his career, with his life story.”

Djokovic, who has five Grand Slam titles, said the doping programme in tennis was sufficient to catch the cheats, though he conceded he hasn’t had a blood test that could detect illegal oxygen-boosting agents for six months.

He will play number 15 Stanislas Wawrinka, who beat American Sam Querrey 7-6 (6), 7-5, 6-4 yesterday, in the fourth round.

Querrey’s loss meant that for the second consecutive year, there will be no American men in the fourth round at Melbourne Park. Last year was the first time no US man reached the fourth round at the Australian Open since 1973 — when no Americans traveled to the tournament.

During yesterday’s match, Djokovic was troubled at times against the wily veteran Stepanek, who mixed up the tempo with a lot of serve-and-volley and some unorthodox shot-making.

Stepanek had Djokovic smiling and acknowledging his winners on some points, frustrated him on others with his constant, stay-in-the-point defence, and even had chair umpire Carlos Bernardes grinning with his over-the-shoulder winner to save one match point near the end.

In yesterday’s last third-round match, fourth-seeded David Ferrer of Spain beat Marcos Baghdatis of Cyprus 6-4, 6-2, 6-3, clinching the one-hour, 57-minute match with an ace.

Elsewhere, fifth-seeded Tomas Berdych of the Czech Republic beat Austria’s Jurgen Melzer 6-3, 6-2, 6-2 and will next play South Africa’s Kevin Anderson, who beat number 22 Fernando Verdasco 4-6, 6-3, 4-6, 7-6 (4), 6-2.

Others advancing included Japan’s Kei Nishikori, who will face Ferrer in the fourth round, and number eight-ranked Janko Tipsarevic, who has a tough next round against number 10 Nicolas Almagro, a 7-6 (3), 7-6 (4), 6-1 winner over number 24 Jerzy Janowicz.

In other women’s matches, Angelique Kerber survived some nervous moments before fending off American teenager Madison Keys 6-2, 7-5 in their third-round match, then got to blow out the candles on a cake to celebrate her 25th birthday.

Local organisers brought a cake onto the court for Kerber immediately after the match and the crowd at Rod Laver Arena sang “Happy Birthday”. She blew out the candles and said thank you to the crowd and to the 17-year-old Keys.

Kerber will next play number 19 Ekaterina Makarova of Russia, who advanced after a tough 6-7 (4), 6-3, 6-4 win over 2007 Wimbledon finalist Marion Bartoli. In the fourth round last year, Makarova beat Serena Williams and was the first of only four women to best the powerful American in 2012. Kerber was the last.

Fourth-seeded Angieszka Radwanska, meanwhile, won her 12th match in a row with a 6-3, 6-1 victory over Britain’s Heather Watson.

Radwanska will now meet 2008 French Open champion Ana Ivanovic, who beat Jelena Jankovic 7-5, 6-3 in a matchup featuring two Serbians who were both formerly ranked number one.

Sixth-seeded Li Na advanced with a 6-4, 6-1 win over number 27 Sorana Cirstea of Romania and will next play number 18 Julia Goerges, who prevented an all-China fourth-round encounter by beating Zheng Jie 6-3, 1-6, 7-5.

Today, Victoria Azarenka and Serena Williams play their third-round matches and the featured night match has second-seeded Roger Federer taking on resurgent Australian Bernard Tomic, who won his first ATP title last week in Sydney after a poor 2012.