Federer and Serena in cruise mode

MELBOURNE // The world's top-ranked tennis players Serena Williams and Roger Federer showed little gratitude to their hosts as they knocked out the last remaining home players to reach the quarter-finals of the Australian Open today. Federer, his confidence and form growing with each match, extended his winning streak against Lleyton Hewitt to 15 with a 6-2, 6-3, 6-4 victory in less than two hours, while Williams showed no mercy against Samantha Stosur, winning 6-4, 6-2 in a little over an hour.

Williams still needs to win three more matches to defend her title but the majority of her main rivals have fallen by the wayside ensuring she will retain her No 1 ranking regardless of what happens over the remainder of the week. She is the only woman in the top five left in a draw that has produced an unexpected lineup of quarter-finalists, including two from China. The nation's sporting revolution has been slow in reaching international tennis. More than two million Chinese play for fun but only a handful take it seriously enough to make a mark on the professional game.

At the forefront of her country's batch of leading players is Zheng Jie, who gave the world a glimpse of the changing face of tennis when she made the semi-finals at Wimbledon two years ago. The 26-year-old has been joined in the quarter-finals time by Li Na, who defeated Denmark's Caroline Wozniacki 6-4, 6-3. It was not an upset of major proportions for Li is ranked 17th in the world, but it was still a surprise as Wozniacki made the final of last year's US Open and was seeded fourth at Melbourne Park.

"Yeah, this is good for us, both players in the quarter-finals," Li said, before jokingly revealing the secret behind their success. "Maybe I eat Chinese food." Wozniacki is a popular figure in Australia but her loss to Li was a victory for the tournament's marketing team who have rebranded the championship as the Grand Slam of Asia/Pacific. Li's next opponent is Venus Williams, who booked her place in the quarter-finals with a 3-6, 6-2, 6-1 win over Italian Francesca Schiavone.

As a former world No 1 and multiple grand slam winner, Venus is entitled to start as favourite although Li can draw confidence from her only previous encounter with the American at the 2008 Beijing Olympics, which she won 7-5, 7-5. "It was good experience for me, for my tennis. But I just want to forget [that], because I will play her again." Venus has never won the Australian Open and time may be running out for her. At 29, she is the oldest woman left in the draw and if she beats Li she could face Serena in the semi-finals.

She was well below her best against Schiavone, dropping the opening set then losing her first service game in the second set without winning a point. But once Venus found her rhythm the contest was over. "I just realised I was rushing a little too much and I just really needed to take my time," Venus explained. There have been few surprises in the men's event and the pattern continued as Serbia's Novak Djokovic and Russia's Nikolay Davydenko both won.

Djokovic, the 2008 champion, sealed his place in the quarter-finals with a 6-1, 6-2, 7-5 win over Poland's Lukasz, the only unseeded player to make the fourth round of the men's draw. "If he's seeded or unseeded, if he comes to the second week of play, he must be a quality player," Djokovic said. Davydenko had to work a lot harder before wearing down Spain's Fernando Verdasco 6-2, 7-5, 4-6, 6-7, 6-3.

The Russian had won his three previous matches in straight sets but was grateful for the workout with Federer next. Federer and Hewitt have been rivals since they were 14 and starting out in the juniors but are now both 28 and married with children. That is where the similarities end and the gulf between the current and former world No1s has never looked wider although Federer remained respectful of the Australian.

"I always knew it would be extremely hard. It was. I'm sweating bullets," Federer said. "He's a great competitor. It's always a pleasure playing him. He's playing really good again, I hope he can keep it up." * Reuters