Pattaya: Sania Mirza dug deep into her reserves to overcome a fighting Anne Keothavong 6-4, 7-5 to progress to the singles quarter-finals of the USD 220,000 Pattaya Open on Thursday.
The unseeded Indian, ranked 111, tamed her giant-killing British rival in a hard-fought second-round match after one hour and 40 minutes of struggle.
Keothavong, ranked 88, had shocked second seed and world number 16 Dominika Cibulkova of Slovakia in the opening round.
Sania also reached the doubles quarter-finals with Australian partner Anastasia Rodionova.
The top-seeded pair routed a hapless French pair of Iryna Bremond and Caroline 6-0, 6-2 in the first round.
They are now up against the local pair of Varatchaya and Varunya Wongteanchai in the last-eight stage match.
In the singles match, Sania served extremely well in the second set and put behind an early break to stage a brilliant comeback.
She saved a crucial break-point in the 11th game and then broke Keothavong for the second time to claim a well-deserved win.
She will now face either Japanese Kimik Date-Krumm or Chinese Taipei qualifier Su-Wei Hsieh in the quarter-finals.
Sania had lost in the qualifiers at this event last year.