They were joined on their way out of the tournament by top-seed Caroline Wozniacki of Denmark.

Wozniacki, who has yet to win a Grand Slam title was left wanting again at Wimbledon after diminutive Slovakian Dominika Cibulkova battled past the world number one in three sets 1-6 7-6 (7-5) 7-5.

Wozniacki has never been past the fourth round here at Wimbledon and was disappointed with the result.

"I did my best and it wasn't good enough," said Wozniacki. "It's disappointing because when you're up 2-0 with a break and have a lot of break points that you don't convert, that's kind of your own fault."

Cibulkova will face Maria Sharapova in the quarter-finals on Tuesday after the 5th-seeded Russian powered past China's Shuai Peng 6-4 6-2.

Defending champion Serena Williams saw her run come to an end with a straight-sets 6-3 7-6 (8-6) loss to 9th-seed Marion Bartoli of France.

Bartoli displayed the sort of tennis that took her to the final here at Wimbledon back in 2007. The Frenchwoman was confidently powering down aces and often out-hitting Serena in many of the gruelling rallies.

Bartoli broke Serena in the sixth game of the first set before clinching the set with an ace on her fifth set point.

The two were evenly matched in the second set until 5-5 when Williams gifted Bartoli a break with two backhand errors to fall behind 5-6.

As in the first set when down at crucial points Serena was able to call on all her fighting abilities and battled back into contention to break back after saving three match points.

In the ensuing tie-break Serena saved another match point but could not stop Bartoli sealing the match at the fifth attempt with an un-returnable powerful first serve.

"Usually during matches when I was playing against some great champions like Serena, I was a bit shy, not showing too much on the court," said Bartoli after the match.

"It's really important for me to believe that I can win the match and act like a winner. This kind of attitude really helped me get through the match."

Minutes after Serena's defeat, Venus took to Centre Court to begin her fourth round match against Tsvetana Pironkova of Bulgaria.

31-year-old Williams lost to Pironkova in the quarter-finals of last year's Championships and could do nothing to prevent that from happening again.

Playing far from her best tennis, Venus slumped to a 6-2 6-3 defeat - exactly the same score line as last year and will have to wait until next year to try and add another Wimbledon title to her collection.

"This was definitely not our [the Williams sisters'] best day. We both envisioned seeing this day going a little bit differently," said Venus.

"We both want each other to win but unfortunately we weren't able to. We rarely lose on the same day."

In other fourth round matches on Monday, fourth-seed Victoria Azarenka defeated Nadia Petrova of Russia 6-2 6-2. Germany's Sabine Lisicki continued her fine run with a 7-6 (7-3) 6-1 win over Czech player Cetkovska. Eighth-seed Petra Kvitova defeated Yanina Wickmayer of Belgium 6-0 6-2 and Austria's Tamira Paszek defeated Russia's Ksenia Pervak in three sets 6-2 2-6 6-3.