Caroline Wozniacki started her first major as the No. 1-ranked woman with a 6-3, 6-4 victory over Argentina's Gisela Dulko on Monday in the Australian Open.

It was the 20-year-old Wozniacki's first victory of the year, following a straight-sets loss to Slovakia's Dominika Cibulkova last week in the Sydney International and exhibition losses to No. 2 Vera Zvonareva and Kim Clijsters in Singapore and Hong Kong.

Wozniacki didn't face a break point in the first set and converted her only chance.

Dulko, the top-ranked doubles player, tested Wozniacki in the second set and pulled level at 4-4 with a service break, but the Danish player broke back immediately and served it out on her second match point after a double-fault on her first.

Wozniacki won six tournaments in 2010, including four of her last six, and can retain the top spot by reaching the semifinals.

"My dream when I was a little girl was to reach No. 1 in the world, and that happened last year. But it's a new year, a new start," she said in a courtside interview. "I'm just looking forward to it."

Earlier on center court, Maria Sharapova won for the first time at Melbourne Park since taking the 2008 title, beating Thai veteran Tamarine Tanasugarn 6-1, 6-3.

Sharapova, the former top-ranked player who missed the 2009 tournament because of a shoulder injury and was ousted in the first round last year by fellow Russian Maria Kirilenko, struggled with her serve and was inconsistent in the second set. After losing the opening service game at love, Sharapova won seven straight games to take a 6-1, 1-0 lead.

The 33-year-old Tamarine, clearly not in peak physical condition, rallied and had a game point on serve for a 4-1 lead, but 14th-seeded Sharapova broke back and regained momentum, winning the last five games.

Even when she was winning, though, Sharapova had trouble finding range with her serve. She had 10 double-faults and five aces.

Nerves had a role in that.

"I definitely felt that in the beginning. I knew I had an early exit last year and didn't want that to happen this year," said Sharapova, who has the goal in Australia of "staying aggressive and little by little trying to get my game better, maybe to where it was a few years ago and maybe better than that."

French Open champion Francesca Schiavone had a couple of stutters before advancing with a 6-7 (4), 6-2, 6-4 victory over Arantxa Parra Santonja of Spain

The sixth-seeded Schiavone had a chance to serve for the match at 5-3 in the third but was broken. The Italian player recovered quickly, breaking Parra Santonja's service in the next game to take the match.

In other women's matches, No. 20 Kaia Kanepi of Estona beat Slovakia's Magdalena Rybarikova 2-6, 6-4, 6-3 and No. 29 Dominika Cibulkova of Slovakia advanced 6-2, 6-7 (4), 6-4 over Germany's Angelique Kerber.

No. 18 Sam Querrey was the first of the men's seeded players eliminated, losing 5-7, 6-2, 3-6, 6-1, 8-6 to Poland's Lukasz Kubot, while No. 12 Gael Monfils rallied from two sets and a break down to beat former world junior champion Thiemo De Bakker.

De Bakker served for the match in the third set but made a series of unforced errors on key points and Monfils capitalized, winning 6-7 (5), 2-6, 7-5, 6-2, 6-1.

No. 26 Juan Monaco of Argentina advanced in straight sets over Simon Gruel, who got a spot in the main draw earlier Monday when Julien Benneteau of France withdrew because of in infected finger on his playing hand.

Defending champion Roger Federer was to play Lukas Lacko of Slovakia in the third match on Rod Laver Arena, where he has won four previous Australian titles.

Federer and top-ranked Rafael Nadal were behaving like best mates at Rod Laver Arena — high-fiving, hugging, shaking hands and laughing at each other's jokes on Sunday night in the exhibition "Rally for Relief" fundraiser for victims of the fatal floods in Australia's northeastern Queensland state. It'll be a completely different story if they're back on the same court in two weeks.

Nadal has won the three Grand Slam titles since Federer's victory here in Australia and is aiming to become the first man since Laver in 1969 to win four straight majors. It's being dubbed the "Rafa Slam."

The pair played on opposite sides of the net, and then played together against Kim Clijsters and Sam Stosur in front of a capacity crowd of 15,000 that paid to watch a host of tennis stars in the fundraiser. Novak Djokovic and Andy Roddick wore microphones and joked with the crowd, playing alongside and against the likes of Caroline Wozniacki and Victoria Azarenka in the celebrity hit-and-giggle exhibition.

Third-seeded Djokovic, the 2008 champion, plays Spaniard Marcel Granollers in the main night match Monday.

Andy Roddick plays Jan Hajek of the Czech Republic on the second showcourt. Following Roddick on Hisense Arena will be fourth-seeded Venus Williams against Italy's Sara Errani, and seven-time Grand Slam winner Justine Henin against Indian qualifier Sania Mirza.