All top seeds made it through to the quarterfinals of the singles event to set up mouthwatering clashes at the Olympic tennis tournament on Wednesday.

World number one Roger Federer of Switzerland beat Czech Tomas Berdych 6-3, 7-6(4) in the third round to revenge an Olympic loss in the Athens Games four years ago.

Spaniard Rafael Nadal, the incoming world number one, was also barely tested in the match against Russian Igor Andreev.

Nadal, who is set to take over the number one spot from Federer after the Olympic tennis event, took a while to find his footing in the beginning but finally had control of the match, outclassing Igor Andreev 6-4, 6-2.

Third seed Djokovic struggled to gain control through the first set, clinching his quarterfinal berth with a 7-6(3), 6-3 win over Mikhail Youzhny in one hour and 36 minutes.

While the world number three Djokovic did not appear on top of his game, he never offered the Russian a shot at breaking his serve.

Youzhny had a brief lead with a mini break in the tiebreaker at 3-2 when Djokovic sailed a forehand crosscourt shot wide, an out call that the Serbian protested. But Djokovic won the next two points and then captured the set when the Russian No. 13 double-faulted on the 10th point.

Youzhny, who made 53 unforced errors in the match, surrendered his serve in the third game to put Djokovic permanently ahead and into the quarterfinals.

"I started slowly. And I think the reason was my late finish last night in doubles. I think I was one of the last players. Our match was really late, one of the last matches that finished. I went to bed around 3:30 in the morning, so I was quite tired to start a match. But then I managed to stay," said the Serb.

"It was very important to win the first set. After it I really served well and put a lot of pressure on him."

Nadal will play 51st ranked Jurgen Melzer from Austria in the quarterfinals, a match expected to be a lopsided one, while the Serbian sensation plays Frenchman Gael Monfils, who upset the No. 7 seed David Nalbandian of Argentina.

Federer will take on American eighth seed James Blake, to whom he never lost in the previous eight meetings.

Blake needed one hour and 15 minutes to see off French 10th Gilles Simon 6-4, 6-2 in third round.

Elsewhere, Athens bronze medalist Fernando Gonzalez beat Olivier Rochus from Belgium 6-0, 6-3 and will meet Frenchman Paul-Henri Mathieu, who beat German 15th seed Nicolas Kiefer 6-3, 7-5.

In women's draw, second seed Jelena Jankovic and sixth seed Dinara Safina overcame respective opponents to set up the most absorbing quarterfinal on Thursday.

"I don't look too far ahead, especially with my injury, and I don't know if I'm going to be on court and do my best," said world number one Jankovic, who is playing with an injury in her right calf.

"Safina has been in great form the last few months, and she's playing some great tennis. I lost to her a couple weeks ago when I just came back from my knee injury, so I really have to play my best tennis if I want to win against her because she's quite strong at the moment."

China's Li Na became the only player to carry home interest in the last eight after coming back from one set down to beat Kaia Kanepi from Estonia 4-6, 6-2, 6-0 in the third round.

In the opening set, Li fired eight winners to just one of the Estonian, but was troubled by her uncharacteristic 31 unforced errors to 17 of Kanepi, losing at 6-4.

Coming into the second set, Li played a consistent game and did not give her opponent any break point, while converting on five of all her 10 chances of breaking in the remaining time.

American Serena Williams started sluggishly before putting together a hard-fought 3-6, 6-3, 6-4 win over talented French teenager Alize Cornet.

In contrast to her sister's struggle, Venus, the double gold medallist in singles and doubles at the Sydney 2000, scored a confident 6-3, 6-2 third round victory over No. 12 seed Victoria Azarenka from Belarus.

Serena, playing in her first Olympic singles event, racked up 48 unforced errors in the match and her serve was broken on three of five occasions.

Although Cornet challenged Williams until the end, exchanging brutally powerful baseline shots, the Frenchwoman eventually surrendered to her mightier opponent, an eight-time Grand Slam champion.

Venus Williams, who won her fifth career Wimbledon title last month, faced a momentary hiccup when she fell behind 3-1 in the early stages of the 70-minute match.

But she pulled her game together to win 11 of the next 13 games to book her place in the quarterfinals.

Serena Williams will take a 4-1 winning record into the quarterfinal against No. 5 seed Elena Dementieva, but the Russian won their last meeting in the final of the 2007 Moscow tournament.

Venus Williams will have to deal with the surprise quarterfinalist Li in the next match. Not unexpectedly, Li will enjoy the support of a very vocal fan base.

Another quarterfinal will see Russian 9th seed Vera Zvonareva play Sybille Bammer of Austria.

(Xinhua News Agency August 14, 2008)