Wimbledon women's tennis champion Maria Sharapova reached the quarterfinals of the Advanta Tennis Championships when her opponent, Jelena Kostanic of Croatia, had to retire.

Sharapova, the third seed, was leading the match, 2-6, 6-4, 3-0, when Kostanic pulled out with a leg strain. The Russian faces the winner of Thursday's match between Jelena Jankovic of Serbia-Montengro and Olympic bronze medalist Alicia Molik of Australia.

Meanwhile, fourth-seeded Jennifer Capriati of the United States has a quarterfinal date against the winner of Thursday's match between Russian sixth seed Vera Zvonareva and Nathalie Dechy of France.

Top seed and defending champion Amelie Mauresmo of France has a second round contest against Iveta Benesova of the Czech Republic. American Amy Frazier plays Nadia Petrova of Russia.

French Open champion Anastasia Myskina plays Paraguay's Rossana Neffa-de Los Rios. American Venus Williams takes on Ukraine's Yuliana Fedak in the evening session.