WIMBLEDON, England -- Wimbledon already has lost its top-four seeded women's players, while the Williams sisters keep rolling toward another sibling final. Roger Federer and Rafael Nadal also are closing in on another title matchup.

Monday's fourth-round play at the All England Club produced more upsets at the top of the women's seedings, but also offered more convincing wins from the champions and title contenders.

Second-seeded Jelena Jankovic, hobbled by a knee injury, fell 6-3, 6-2 to Tamarine Tanasugarn. No. 4 Svetlana Kuznetsova, the 2004 U.S. Open champion, lost 6-4, 1-6, 7-5 to 19-year-old Agnieszka Radwanska.

With top-seeded Ana Ivanovic and No. 3 Maria Sharapova eliminated last week, none of the top four seeded women reached the quarterfinals -- the first time that's happened at any Grand Slam tournament in the 40-year history of the Open era.

The highest women's seeded player left is No. 5 Elena Dementieva, who cruised to a 6-2, 6-1 win over Shahar Peer. Only three of the top 14 seeded women are left.

The other two are the Williams sisters.

Defending champion and seventh-seeded Venus Williams beat Russian teenager Alisa Kleybanova 6-3, 6-4, while two-time winner and No. 6 Serena downed Bethanie Mattek -- the only other American left in the men's or women's draw -- 6-3, 6-3.

Between them, four-time champion Venus and two-time winner Serena have won six of the last eight women's singles titles at Wimbledon. They're in opposite halves of the draw and could meet in the final Saturday. The Williams sisters faced each other in the 2002 and 2003 finals, with Serena winning both.

"Both of us have an opportunity to live our dream, so for us it's a plus," Venus Williams said.

In men's play, Federer swept Lleyton Hewitt -- the last man to win the title before his run of five straight titles -- 7-6 (7), 6-2, 6-4 on Centre Court to extend his winning streak on grass to 63 matches and 38 in a row at the All England Club.

Federer will next face the last player to beat him on grass and at Wimbledon -- Croatian Mario Ancic, who won in the first round in 2002. Ancic came from two sets down Monday to beat Fernando Verdasco 3-6, 4-6, 6-3, 6-4, 13-11. The final set alone lasted 1 hour, 35 minutes.

No. 2-ranked Nadal, runner-up to Federer the last two years, overcame an injury scare in the second game of the match and beat Mikhail Youzhny 6-3, 6-3, 6-1.

No. 10-seeded Marcos Baghdatis, a semifinalist in 2006 and quarterfinalist last year, squandered three match points in the fifth set. The Cypriot lost 5-7, 6-2, 3-6, 7-6 (4), 8-6 to Feliciano Lopez.

Also advancing among the men was former No. 1 Marat Safin, who beat No. 13 Stanislas Wawrinka in four sets.