Sixth-seeded Olga Poutchkova beat Olivia Sanchez 7-5, 6-1 after a two-hour rain delay to reach the quarter-finals for the fourth consecutive tournament.

The 55th-ranked Mirza, who became the first female from India to win a WTA event at the Hyderabad (India) Open last year, broke for a 6-5 lead in the second set.

Sun Tiantian defeated Tatiana Poutchek 6-4, 6-4, and Victoria Azarenka beat Dominika Cibulkova 6-4, 6-4.

``I served better and played better on key points,'' Azarenka said.