WIMBLEDON, ENGLAND (AP) - After three of the biggest names in women's tennis were sent home early, the big four in the men's game kept on rolling in their chase for the Wimbledon title.
A question mark, however, hangs over the fitness of defending champion Rafael Nadal, who injured his left foot and is unsure if he'll be fit for Wednesday's quarterfinals.
Monday's fourth-round matches _ featuring the appearance of Prince William and new bride Kate in the Royal Box _ produced a series of upsets in the women's draw that knocked out the Williams sisters and top-seeded Caroline Wozniacki.
For awhile, it looked like six-time champion Roger Federer and two-time winner Nadal might be in danger, too, before they pulled through to reach the last eight along with No. 2 Novak Djokovic and No. 4 Andy Murray.
For the first time since 2006, there won't be a Williams in the women's quarters. The sisters _ who have won nine of the last 11 Wimbledon titles and faced each other in four finals _ were eliminated in quick succession.
First to go was defending champion and four-time winner Serena, beaten 6-3, 7-6 (6) by Marion Bartoli of France, cutting short the American's return to Grand Slam tennis after nearly a year out with serious health problems.
Then, older sister and five-time champ Venus was ousted 6-2, 6-3 by Tsvetana Pironkova _ the exact same score of the Bulgarian's win in last year's quarterfinals.
"Definitely not our best day," Venus said. "I think we both envisioned seeing this day going a little bit different. .. We rarely lose on the same day."
In fact, the last time that happened at a Grand Slam was in 2008, when the sisters were ousted in the third round of the French Open.
Both sisters came into this year's Wimbledon short on match play. Venus was out for nearly five months with a hip injury, while Serena missed nearly a year after two foot operations and treatment for blood clots in her lungs. They both returned to action in Eastbourne two weeks ago.
This was Venus' earliest exit from Wimbledon since 2006 and Serena's earliest loss here since 2005.
"I think I did really well just being able to come back and play and win some matches, and just really play tough," Serena said. "Even today I lost, but I was able to kind of hang in there and play tough. And I can only get better. That can potentially be really scary, because I can only go up from here and I can just do so much more."
Serena, who had dropped to No. 25 in the WTA rankings during her layoff, will now plummet to around 175th.
The current No. 1-ranked woman, Wozniacki, fell 1-6, 7-6 (5), 7-5 to No. 24 Dominika Cibulkova of Slovakia, the latest stinging defeat for a player yet to win a Grand Slam title. The Dane has only even reached one major final, losing to Kim Clijsters at the 2009 U.S. Open, yet will remain No. 1 at least until early August.
"I don't really care what people think or say or do," Wozniacki said. "I cannot really do anything now. I did my best and it wasn't good enough."
The top name remaining in the women's field is sixth-seeded Maria Sharapova of Russia, the 2004 champion who made it to the quarterfinals for the first time since 2006 by beating China's Peng Shuai 6-4, 6-2.
For the first time since 1913, the women's quarterfinal lineup features eight European players, all from different countries.
In Tuesday's matches, it will be Sharapova vs. Cibulkova; No. 9 Bartoli vs. wild card Sabine Lisicki (Germany); No. 8 Petra Kvitova (Czech Republic) vs. No. 32 Pironkova; and No. 4 Victoria Azarenka (Belarus) vs. Tamira Paszek (Austria).
The men's quarters will be played Wednesday, with Nadal vs. No. 10 Mardy Fish of the United States; Murray vs. unseeded Feliciano Lopez of Spain; Federer vs. No. 12 Jo-Wilfried Tsonga of France; and Djokovic vs. 18-year-old Australian qualifier Bernard Tomic, the youngest men's quarterfinalist since Boris Becker in 1986.
Nadal said he would undergo an MRI scan to determine the extent of his foot injury. The Spaniard said he initially thought he might have broken his foot and would have to retire from his match against Juan Martin del Potro, which he went on to win 7-6 (6), 3-6, 7-6 (4), 6-4.
"I felt something that like crushed there in the back of the foot outside," Nadal said.
The injury came as Nadal hit a forehand in the game before the first-set tiebreaker. He called for a medical time-out and a trainer sprayed the foot and taped it up. He limped through much of the tiebreaker but seemed unhindered the rest of the way.
Nadal said he was "worried" whether he would be fit for Wednesday's match against Fish.
"I cannot predict the future," he said. "Let's see what's going on and let's see how the MRI looks. And after, let's see if we have the chance to recover for Wednesday. I don't know."
Federer lost his first set of the tournament before coming back to down Mikhail Youzhny 6-7 (5), 6-3, 6-3, 6-3 to reach his 29th successive Grand Slam quarterfinal. Extending his career record against the Russian to 11-0, Federer also won his 100th career match on grass.
Murray swept Richard Gasquet of France 7-6 (3), 6-3, 6-2 _ then took a majestic bow to the Royal Box, where Wiliam and Kate joined the rest of the crowd in a standing ovation. Murray is trying to become the first British man to win the title at the All England Club since Fred Perry in 1936.
Murray met the royal couple after the match and offered a sheepish apology.
"If I'd known they were coming, I would have shaved," the Scot said with a smile. "I was thinking to myself as I came off I was sweaty and very hairy. I said to them, 'I'm sorry, I'm a bit sweaty.' But it was really nice."