<p>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 Serena showed no mercy against Samantha Stosur, winning 6-4, 6-2 in a little over an hour. <br /><br />Serena 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 number one 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 quarterfinalists, including two from China. 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 semifinals at Wimbledon two years ago. <br /><br />The 26-year-old has been joined in the quarterfinals time by Li Na, who defeated Denmark's Caroline Wozniacki 6-4, 6-3. <br /><br />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. <br /><br />Li's next opponent is Venus Williams, who booked her place in the quarterfinals with a 3-6, 6-2, 6-1 win over Italian Francesca Schiavone. <br /><br />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 semifinals. 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. <br /><br />Victoria Azarenka of Belarus reeled off 10 games in row in an extraordinary turnaround to beat Russia's Vera Zvonareva 4-6, 6-4, 6-0 to make it to the quarterfinals for the first time.<br /><br />Azarenka had never taken a set off Zvonareva in their four previous meetings and looked to be heading for another quick defeat when she lost the opening set and went a break behind in the second. <br /><br />But the 20-year-old, ranked seventh in the world, turned the match around by winning all the remaining games to seal victory after nearly three hours. Azarenka will take on Serena in the last-eight clash. 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. <br />Djokovic, the 2008 champion, sealed his place in the quarterfinals 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. Davydenko had to work a lot harder before wearing down Spain's Fernando Verdasco 6-2, 7-5, 4-6, 6-7, 6-3. <br /><br />Australian Open fourth round results (prefix denotes seeding): Men’s singles: 1-Roger Federer (Sui) bt 22-Lleyton Hewitt (Aus) 6-2, 6-3, 6-4; 6-Nikolay Davydenko (Rus) bt 9-Fernando Verdasco (Spa) 6-2, 7-5, 4-6, 6-7 (5-7), 6-3; 3-Novak Djokovic (Serb) bt Lukasz Kubot (Pol) 6-1, 6-2, 7-5.<br /><br />Women's singles: 7-Victoria Azarenka (Blr) bt 9-Vera Zvonareva (Rus) 4-6, 6-4, 6-0; 1-Serena Williams (US) bt 13-Samantha Stosur (Aus) 6-4, 6-2; 16-Li Na (Chn) bt 4-Caroline Wozniacki (Den) 6-4, 6-3; 6-Venus Williams (US) bt 17-Francesca Schiavone (Ita) 3-6, 6-2, 6-1.</p>
<p>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 Serena showed no mercy against Samantha Stosur, winning 6-4, 6-2 in a little over an hour. <br /><br />Serena 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 number one 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 quarterfinalists, including two from China. 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 semifinals at Wimbledon two years ago. <br /><br />The 26-year-old has been joined in the quarterfinals time by Li Na, who defeated Denmark's Caroline Wozniacki 6-4, 6-3. <br /><br />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. <br /><br />Li's next opponent is Venus Williams, who booked her place in the quarterfinals with a 3-6, 6-2, 6-1 win over Italian Francesca Schiavone. <br /><br />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 semifinals. 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. <br /><br />Victoria Azarenka of Belarus reeled off 10 games in row in an extraordinary turnaround to beat Russia's Vera Zvonareva 4-6, 6-4, 6-0 to make it to the quarterfinals for the first time.<br /><br />Azarenka had never taken a set off Zvonareva in their four previous meetings and looked to be heading for another quick defeat when she lost the opening set and went a break behind in the second. <br /><br />But the 20-year-old, ranked seventh in the world, turned the match around by winning all the remaining games to seal victory after nearly three hours. Azarenka will take on Serena in the last-eight clash. 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. <br />Djokovic, the 2008 champion, sealed his place in the quarterfinals 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. Davydenko had to work a lot harder before wearing down Spain's Fernando Verdasco 6-2, 7-5, 4-6, 6-7, 6-3. <br /><br />Australian Open fourth round results (prefix denotes seeding): Men’s singles: 1-Roger Federer (Sui) bt 22-Lleyton Hewitt (Aus) 6-2, 6-3, 6-4; 6-Nikolay Davydenko (Rus) bt 9-Fernando Verdasco (Spa) 6-2, 7-5, 4-6, 6-7 (5-7), 6-3; 3-Novak Djokovic (Serb) bt Lukasz Kubot (Pol) 6-1, 6-2, 7-5.<br /><br />Women's singles: 7-Victoria Azarenka (Blr) bt 9-Vera Zvonareva (Rus) 4-6, 6-4, 6-0; 1-Serena Williams (US) bt 13-Samantha Stosur (Aus) 6-4, 6-2; 16-Li Na (Chn) bt 4-Caroline Wozniacki (Den) 6-4, 6-3; 6-Venus Williams (US) bt 17-Francesca Schiavone (Ita) 3-6, 6-2, 6-1.</p>
