By STEVEN WINE
AP Sports Writer
WIMBLEDON, England -- While Roger Federer glided to another victory on Centre Court, and Rafael Nadal won despite a scary stumble on Court 1, the Williams sisters found themselves playing back to back Monday on cozy, clattery Court 2, known as the "Graveyard of Champions."
What in the name of lawn tennis were they doing out there?
"It wasn't what I would have liked to see," Serena Williams said. "Initially I thought, 'OK, is this the right schedule?' I thought maybe there was a mistake."
The sisters' mother and coach, Oracene Price, suspected more than a mere mistake by tournament organizers.
"I guess they wanted to put them on the jinx court so they could lose," Price said.
The sisters said Wimbledon gives men preferential treatment in court assignments, while Federer came to the defense of the All England Club, and the tournament referee said there was no intent to slight anyone.
Even after Venus and Serena spent the day at the Graveyard, their title hopes remained very much alive. They're defying the trend in a women's tournament that, by one measure, ranks as the most upset-filled on record.
Four-time champion Venus played first, making a high-noon entrance on the court known for its history of upsets and beating Alisa Kleybanova 6-3, 6-4. Ninety minutes later, two-time Serena joined her older sister in the quarterfinals by defeating American Bethanie Mattek 6-3, 6-3.
Neither sister has lost a set in the tournament, and the chances of a sibling showdown in the final keep improving as a wave of upsets take out other title contenders. The fourth round claimed No. 2-seeded Jelena Jankovic and No. 4 Svetlana Kuznetsova, leaving No. 5 Elena Dementieva as the highest-seeded survivor among the final eight.
The elimination before the quarterfinals of the women seeded Nos. 1-4 has never previously happened at Wimbledon since the tournament began keeping such records in 1927. It's the first time it has happened at any Grand Slam event in the 40-year Open era.
"Every player is ready to play, especially at these Slams," Venus Williams said. "Everyone comes out with double vengeance, so you just have to be ready."
Jankovic, slowed by a knee injury she suffered in the previous round, lost to No. 60-ranked Tamarine Tanasugarn 6-3, 6-2. Kuznetsova was beaten by No. 14-seeded Agnieszka Radwanska 6-4, 1-6, 7-5.
Their defeats ensure Ana Ivanovic of retaining the No. 1 ranking next week, even though she was beaten by Zheng Jie in the third round. The No. 133-ranked Zheng, who needed a wild card to enter the tournament, became a first-time Grand Slam quarterfinalist by beating No. 15-seeded Agnes Szavay 6-3, 6-4.
Alla Kudryavtseva, who upset No. 3-seeded Maria Sharapova in the second round, was eliminated by Nadia Petrova 6-1, 6-4.
Tanasugarn, a first-time Grand Slam quarterfinalist at age 31, will play Venus Williams on Tuesday. The 19-year-old Radwanska will face Serena Williams.
Almost as unpredictable is the men's draw, with eight of the top 10 players eliminated. But the No. 1-ranked Federer and No. 2 Nadal remain on course to meet in the final for the third consecutive year.
While Federer beat 2002 champion Lleyton Hewitt for the 12th time in a row Monday, Nadal hurt his right leg against Mikhail Youzhny and stopped in the middle of the second game for treatment by a trainer.
Nadal slipped on worn turf behind the baseline while stretching for a shot, and his right leg bent awkwardly. He said he felt a crack behind the knee.
"I felt a little bit pain," he said. "I was a little bit scared."
After the trainer wrapped Nadal's leg below the knee, the Spaniard showed no sign the injury bothered him the rest of the way, winning 6-3, 6-3, 6-1.
"Right now I am feeling better," Nadal said an hour after the victory. "Tomorrow we will see how I wake up. But hopefully going to be fine."
Nadal will next play No. 12-seeded Andy Murray, trying to become the first British man to win Wimbledon since 1936. He thrilled a partisan Centre Court crowd by completing a comeback win just before dark against No. 8 Richard Gasquet, 5-7, 3-6, 7-6 (3), 6-2, 6-4.
Marat Safin reached a Grand Slam quarterfinal for the first time since winning the 2005 Australian Open, beating No. 13 Stanislas Wawrinka 6-4, 6-3, 5-7, 6-1. Safin's opponent Wednesday will be No. 31 Feliciano Lopez, who overcame three match points to defeat No. 10 Marcos Baghdatis 5-7, 6-2, 3-6, 7-6 (4), 8-6.
Federer will next play the last man to beat him at Wimbledon, Mario Ancic. Federer overcame some shaky moments in the first-set tiebreaker to defeat Hewitt 7-6 (7), 6-2, 6-4, while Ancic outlasted Fernando Verdasco 3-6, 4-6, 6-3, 6-4, 13-11.
Since losing to the big-serving Ancic in the first round in 2002, Federer has won 63 consecutive grass-court matches, including 38 at Wimbledon.
"I completely underestimated him back in 2002," Federer said. "What it taught me was not to underestimate any opponent."
That may be the biggest challenge in the next two rounds for the Williams sisters, who have won six of the past eight Wimbledon titles and are dominating again this year. If the Graveyard of Champions can't stop them, what will?
Court 2 has no tombstones, but the names of losers there includes such former champions as Pete Sampras, Andre Agassi, John McEnroe, Jimmy Connors -- and both Williams sisters.
There are no replay reviews on Court 2, where the scoreboard is manually operated. There are no seats behind one baseline and only three rows behind the other. Spectators can hear players muttering to themselves, and the soundtrack for matches also includes cheering from other courts and noise from the nearby dining area for players.
"I don't think I've ever played a fourth-round match on a court like that in my career," Serena Williams said.
With all 16 fourth-round matches on the schedule Monday, tournament referee Andrew Jarrett said it was unavoidable that some leading players would be assigned to outer courts. Serena and Venus found themselves back on Court 2 for their evening doubles match, which they also won to reach the quarterfinals.
The tempest about the schedule was defused somewhat because the sisters swept all three matches, and defending champion Venus at first said she had no complaint. But when asked if Wimbledon slights the women when deciding court assignments, she said yes.
Regarding Federer, Serena said, "I haven't seen him on Court 2 in, like, six years."
She's close: He last played there in the 2003 quarterfinals.
Federer said he didn't think the tournament was being disrespectful of anyone. He remembers Sampras losing on the Graveyard in his final Wimbledon match in 2002.
"Pete played on Court 2 after winning seven years," Federer said. "Who deserves what here? It's the club who decides in the end.
"I wouldn't be disappointed if they put me on Court 2. ... Sometimes it's also kind of cool. You're closer to the crowds. It's kind of a different feeling out there."
The Williams sisters might be glad to know the days are numbered for the Graveyard of Champions. As part of a project to renovate the outer courts, a new Court 2 opens next year, while the Graveyard will become Court 3 in 2009 -- meaning fewer marquee matches -- and will eventually be torn down.
In the meantime, Venus has been assigned to the Court 1 stadium Tuesday. Serena is to play on Centre Court, where fans may find them both Saturday.