Impressive Serena steps up defence at Melbourne

Defending champion Serena Williams issued an ominous warning to her Australian Open rivals as the tournament's big names started flexing their muscles yesterday.

Williams was not quite at the top of her formidable powers but was still impressive on a day when Andy Roddick, Lindsay Davenport, Maria Sharapova and Justine Henin-Hardenne all recorded straight set wins.

Williams had appeared to be struggling for fitness and form as she stumbled to a three-set victory over Li Na in the opening round, but her aggressive 49-minute 6-3 6-1 destruction of the unseeded Camille Pin dispelled any concerns about her game.

"Everyone's a threat but I'm real serious and I'm here to be a threat as well," she told a news conference.

Williams's main rivals in the top half of the women's draw all made it through safely, while the bottom half of the men's draw was opened up with the loss of three more seeds.

Robby Ginepri, Radek Stepanek and Tomas Berdych all made early exits, leaving Andy Roddick and David Nalbandian as the favourites to meet in the semi-finals.

Second seed Roddick outslugged South African serve-and-volleyer Wesley Moodie 7-5 6-3 6-2 to remain unbeaten this year following his win in the Kooyong Classic while Nalbandian eliminated Stanislas Wawrinka in a night match 6-4 3-6 6-4 6-2.

"There's no such thing as an open draw," Roddick said. "If there's one thing we've learned by seeds getting knocked out, it proves anybody can play."

World number one Davenport booked a third-round encounter against 25th seed Maria Kirilenko with a hard-fought 7-6 6-3 victory over Karolina Sprem.

The Californian was not at her best but was able to raise her game when it mattered.

On a day when several leading women's seeds scored impressive wins, 2004 champion Henin-Hardenne, of Belgium, beat Hana Sromova 7-6 6-1 to confirm her position as tournament favourite.

The Czech provided eighth seed Henin-Hardenne with some stubborn resistance in the opening set but her challenge faded quickly when she rolled her left ankle and crashed to the court.

Henin-Hardenne has replaced Kim Clijsters as the bookmakers' favourite to win the title after a brilliant start to the season. She is yet to drop a set in her two matches so far but said winning wasn't as easy as it used to be.

"We have to be focused in every match because all these players, they want to beat us and they want to be at our place," she said.

"We need to be one hundred per cent all the time."

The fourth seeded Sharapova led a powerful group of five Russian women, including 2004 US Open champion Svetlana Kuznetsova and sixth seed Nadia Petrova, into the next round.

The 2004 Wimbledon champion showed little sign of the shoulder injury that had threatened to derail her chances as she ground out a 6-1 7-5 victory over Ashley Harkleroad.

Laura Granville joined Williams and Davenport as the last three Americans in the top half of the women's draw after she beat giant-killer Tszvetana Pironkova.

The Bulgarian teenager stunned Venus Williams in the first round but crashed back to earth with a 7-5 6-2 defeat to Granville.

Croatian Davis Cup hero Ivan Ljubicic limped into the third round with a 7-5 6-2 6-1 win over Philipp Kohlschreiber.

The seventh seed Ljubicic needed treatment for an ugly blister on the little toe of his left foot.

He is drawn to meet Roddick in the quarter-finals while Nalbandian faces a fellow Argentine after eighth seed Gaston Gaudio posted an efficient 6-3 6-2 6-3 defeat of German Lars Burgsmuller.