Sania Mirza battled into the quarter-finals of the Sunfeast Open even as Australia's seventh seed Nicole Pratt was upset in the second round in Kolkata on Thursday.

After a close first set, Sania posted a 7-5, 6-3 win over Germany's Sandra Kloesel to set up a clash with fourth seed Aravane Rezai of France, a 6-2, 6-1 winner over Tatiana Poutchek of Belarus.

Sania's 27 winners finally clinched the issue in her favour in a match that saw more service breaks than holds from the players.

Earlier, Russian Olga Poutchkova scalped Pratt, while Uzbek qualifier Iroda Tulyaganova, now on a comeback trail after an injury-induced lay-off, shut out Australian Casey Dellacqua to enter the quarter-finals.

Veteran Pratt went down 2-6, 6-2, 2-6 to Poutchkova in a second round battle before a modest crowd at the Netaji Indoor Stadium.

The Russian girl will clash for a semi-final berth with Italian Alberta Brianti, who staved off a tough challenge from Indonesian girl Angelique Widjaja in a three-setter, winning 7-6 (9-7), 3-6, 6-3.

Tulyaganova, a former world number 16, made short work of Dellacqua 6-3, 6-2 to settle for a last eight fight with Alla Kudryavtseva of Russia, who stormed past Czech Republic's Hana Sromova 6-2, 6-0 in another second round match.

Dellacqua, who had stunned second seed and last year's losing finalist Karolina Sprem of Croatia in the opening round, saw her service desert her as the Uzbek wrapped up the centre court contest in 71 minutes.

Tulyaganova, now with a world ranking of 346 as against the Aussie's 180, broke in the second game of the match, but suffered the same fate in the very next game.

However, the Uzbek took the set in 31 minutes by demolishing Dellacqua's serve in the fourth and sixth games.