DOHA, Qatar — Australian Open champion Maria Sharapova reached the Qatar Open quarterfinals with a 6-2, 6-2 victory over Tamarine Tanasugarn of Thailand today.

The fourth-seeded Russian, who won in 2005, will play Caroline Wozniakci of Denmark tomorrow. Wozniakci ousted Anabel Medina Garrigues of Spain 3-6, 7-6 (3), 6-3.

"I played her in an exhibition match sometime back," Sharapova said of Wozniakci. "She is an upcoming player and it should be a good match."

Second-seeded Svetlana Kuznetsova was upset by Sybille Bammer and sixth-seeded Venus Williams lost to Dominika Cibulkova.

Cibulkova used strong baseline play and broke serve twice in both sets to defeat Williams 6-3, 6-3 in their first meeting.

"This is the best win of my career," the 18-year-old Cibulkova said. "Today, I played my game and beat my favorite player. I admired her as a child."

The 15th-seeded Bammer overcame strong winds to win 6-3, 7-6 (8). Bammer broke Kuznetsova's serve three times in the first set, and both players had four breaks in the second.

"It is always great to beat a top-10 player," Bammer said. "She is a good player with a lot of ability. The conditions were terrible to play. But we have to play in such conditions no matter what."

Also, third-seeded Jelena Jankovic beat Ai Sugiyama 6-1, 6-2 and will play Li Na, who defeated 12th-seeded Shahar Peer 6-1, 6-3. Vera Zvonareva topped 11th-seeded Dinara Safina 7-5, 6-3.

Top-seeded Ana Ivanovic pulled out of the tournament before her third-round match against Agnieszka Radwanska after injuring her left yesterday.