Top seed Martina Hingis of Switzerland opens defense of her title tonight against qualifier Nadejda Petrova of Russia.

Americans Lindsay Davenport and Serena Williams, who squared off in Sunday's final at the estyle.com Classic, also will seek berths in the third round.

Looking to end a four-month title drought, the second-seeded Davenport takes on qualifier Justine Henin of Belgium. Williams, seeded fourth, begins her quest for a second straight title as she faces former top-10 player Patty Schnyder of Switzerland.

Hingis has had mixed results in her first two summer hardcourt events. She reached the quarterfinals at the Acura Classic two weeks ago before falling to Williams last week in the semifinals.

The 19-year-old has won four titles this season, including the Ericsson Open on hard courts, and has reached the finals at three other hardcourt events, including the Australian Open.

Last year, Hingis ended Monica Seles' four-year reign at this event with a 6-4, 6-4 victory.

Davenport failed to win each of the three summer hardcourt events in her home state of California.

The 24-year-old Davenport lost to Serena Williams' older sister Venus in the final at Stanford, California three weeks ago. She followed that with a second-round loss to Russia's Anna Kournikova at San Diego before falling to Serena Williams in the final on Sunday in Los Angeles.

Ranked second in the world behind Hingis, Davenport has won two titles this season, both on hard courts. One of those came at the Australian Open in January.

Serena Williams, who will defend her U.S. Open title in two weeks, will look to extend the recent dominance that she and her sister have displayed over the last six weeks.

Venus Williams captured three straight events before Serena extended the tournament winning streak of the Williams sisters to four with last week's triumph in Los Angeles.

In other seeded action, eighth seed Sandrine Testud of France meets Ruxandra Dragomir of Romania; ninth seed Amanda Coetzer of South Africa faces Magdalena Maleeva of Bulgaria; and 10th seed Julie Halard-Decugis of France encounters Sandra Nacuk of Yugoslavia.

Also, No. 11 Anna Kournikova of Russia goes against Sabine Appelmans of Belgium; No. 13 Jennifer Capriati of the United States, the 1991 champion, battles Virginia Ruano-Pascual of Spain; and No. 16 Amy Frazier of the United States faces Gala Leon Garcia of Spain tonight.

On Tuesday, third seed Conchita Martinez of Spain, sixth seed Anke Huber of Germany, seventh seed Aranxta Sanchez-Vicario of Spain and No. 15 Chanda Rubin of the United States advanced to the third round.

Fifth seed Nathalie Tauziat of France was eliminated by Anne Kremer of Luxembourg in straight sets.

This tournament began in 1892 and offers a $166,000 first prize.

It is the last year the event will be known as the du Maurier Open because of recently passed laws barring tobacco companies from sponsoring sports events. Next year it will be called the Roger's AT&T Canada Cup.