Venus Williams, the third seed and last year's runner-up, routed ninth seed and fellow teenager Anna Kournikova of Russia, 6-2, 6-2, to earn a spot in Friday's quarterfinals. Younger sister Serena, the sixth seed, upended No. 13 Irina Spirlea of Romania, 6-2, 6-3.

Serena Williams lost to her older sister in the final of the Lipton Championships in March. In order to set up a rematch with Venus, the younger Williams must defeat the top-seeded Hingis on Friday. Hingis disposed of American Corina Morariu, 6-1, 6-4, and will look to avenge her semifinal loss to Serena Williams at the Lipton Championships.

Fresh off winning her first claycourt title last week in Hamburg, Germany, Venus Williams will have to beat No. 11 Dominique Van Roost of Belgium in order to set up a possible matchup with her younger sister. Van Roost eliminated seventh seed Nathalie Tauziat of France, 6-4, 7-6 (7-2).

Three seeded Frenchwomen advanced in the bottom half of the draw, but unseeded Sylvia Plischke of Austria provided the biggest upset of the tournament, stunning second seed Arantxa Sanchez-Vicario of Spain, 6-4, 6-1.

Fourth seed Mary Pierce, the 1997 champion, outdueled four-time champion and 15th seed Conchita Martinez of Spain, 4-6, 6-0, 7-6 (7-2). On Friday, Pierce will face eighth seed Sandrine Testud, who defeated Anna Smashnova of Israel, 7-5, 6-1.

Tenth seed Amelie Mauresmo rounded out a trio of Frenchwomen in the quarterfinals. For the second straight day, Mauresmo dropped the first set before coming back to win. Today the Australian Open runner-up rallied past fifth seed Patty Schnyder of Switzerland, 5-7, 6-2, 6-4.

Hingis, 18, improved to 28-4 this season with her victory today. She has won three singles titles in 1999, including her third straight Australian Open. Last month, Hingis was successful in her claycourt season debut, defeating Kournikova to capture the Family Circle Cup in Hilton Head, South Carolina.

Sanchez-Vicario had fared well in her last two claycourt events after being sidelined for three months with a wrist injury. She won her first title of the year at the Egypt Classic two weeks ago and lost to Venus Williams in the semifinals at Hamburg. Sanchez-Vicario will defend her French Open title in three weeks.

First prize is $150,000.