Caroline Wozniacki moved into the Australian Open quarterfinals with a 6-3, 6-4 win over Anastasija Sevastova on Sunday and is just one win from ensuring she’ll retain the No. 1 ranking.

The 20-year-old Dane, playing her first major with the top ranking, finished off Sevastova with a powerful forehand winner in 1 hour, 20 minutes to advance to the quarterfinals at Melbourne Park for the first time. She’ll keep her top ranking just by reaching the semifinals.

She wants more than that, though. She’s aiming for a first Grand Slam title.

Wozniacki lost an early service game to her Latvian rival and was down a break but rallied to win six straight games to close the set and open the second with a service break.

But 46{+t}{+h}-ranked Sevastova rallied and the pair traded breaks until Wozniacki regained control and completed a set - she has now reached the quarterfinals at all four majors.

And she’s navigated some troublesome ground. The WTA reports that only one of the last five women to be ranked No. 1 went beyond the first round in the first major they played with the top ranking.

Men’s No. 1 Rafael Nadal kept his bid for a Rafa Slam on track, and ended Australia’s last hope in the tournament, with a 6-2, 7-5, 6-3 win over 18-year-old wild card Bernard Tomic in the third round on Saturday night.

He extended his Grand Slam streak to 24 consecutive match wins, but said he’s not feeling in peak shape.

He was feeling the lingering effects of an illness that slowed him down at the start of the year, and was sweating and feeling more tired than usual during matches.

“I was perfect when I started the season. I was playing perfect and I was feeling perfect physically,” he said. “In Doha, I had that problem. I wasn’t feel very well. Have fever and these things. “Seems like after that my body is still not perfect.”

The last two Australians went out in consecutive night matches on Rod Laver Arena on a day which attracted a record crowd for the Australian Open - 77,121 across day and night sessions.

French Open finalist Sam Stosur lost 7-6 (5), 6-3 to No. 25 Petra Kvitova. It hasn’t been a good tournament for Australia, which hasn’t produced a homegrown winner of the national championship in more than 30 years.

In fact, it hasn’t been a good tournament for any of the countries that host the four majors.

John Isner went out in a 4-6, 6-2, 6-7 (5), 7-6 (2), 9-7 loss to No. 15 Marin Cilic late Saturday, leaving Andy Roddick as the only American in the tournament.

“I didn’t want to go out in the round of 32 - it stinks,” said Isner, who is famous for his epic encounter against Nicolas Mahut at Wimbledon last year that finished 70-68 in the fifth and was the longest tennis match in history. “It’s going to be tough to sleep.”

Roddick plays 19{+t}{+h}-seeded Stanislas Wawrinka of Switzerland in the fourth round on Sunday night.

There’s no French players left in the men’s or women’s draws after Alize Cornet’s loss to Kim Clijsters. And there’s only one Brit - 2010 runner-up Andy Murray beat Guillermo Garcia Lopez comfortably Saturday and has only conceded 17 games en route to the round of 16.

China has more players in the fourth round, with No. 9 Li Na playing No. 8 Victoria Azarenka on Sunday and Peng Shuai advancing Saturday. And there’s a Canadian in the fourth round of a major for the first time in a dozen years - big serving 20-year-old qualifier Milos Raonic upset No. 10 Mikhail Youzhny 6-4, 7-5, 4-6, 6-4.

Other men advancing included two-time French Open finalist Robin Soderling, seeded fourth, No. 7 David Ferrer and No. 11 Jurgen Melzer.

On the women’s side, U.S. Open champion Clijsters beat Cornet 7-6 (3), 6-3, spoiling the Frenchwoman’s 21st birthday, and moving a step closer to back-to-back majors.

No. 2 Vera Zvonareva and No. 12 Agnieszka Radwanska advanced, as did No. 22 Flavia Pennetta, who ousted No. 10 Shahar Peer.

Defending champion Roger Federer will continue his quest for a fifth Australian Open title in a fourth-round match against Tommy Robredo on Sunday, when 2008 winner Novak Djokovic takes on Nicolas Almagro of Spain.

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