Top-seeded Amelie Mauresmo of France has lost her opening match but No. 2 Maria Sharapova of Russia was a winner at the season-ending WTA Championships tennis tournament in Madrid, Spain.

Fifth-seeded Nadia Petrova of Russia defeated Mauresmo 6-2, 6-2 on Tuesday, while Sharapova topped seventh-seeded countrywoman Elena Dementieva, 6-1, 6-4. In the last match, number-three Justine Henin-Hardenne of Belgium defeated eighth-seeded Swiss player Martina Hingis, 6-2, 6-7, 6-1.

The round-robin tournament features the top-eight ranked women in the world separated into two groups.

Mauresmo and Petrova are in the Yellow Group along with Henin-Hardene and Hingis. The Red Group is comprised of three Russian players: Sharapova, fourth-ranked Svetlana Kuznetsova and Dementieva. They are joined by fifth-seeded Kim Clijsters of Belgium.

It's the first time at this event three players, Mauresmo, Sharapova and Henin-Hardenne, are battling to finish the year with the world number-one ranking. It is also the first time since the elite season-ending tournament debuted in 1972 that no Americans are competing.

Some information for this report provided by AP.