Kim Clijsters [Images] continued her run of superb form on the U.S. hardcourt season while India's Sania Mirza [Images] provided the upset of the second round at the San Diego Classic on Wednesday.

Clijsters won her 19th successive match on the U.S. hardcourts this year with a 6-3, 6-1 victory over Poland's Marta Domachowska, while Mirza capitalised on Nadia Petrova's sore elbow to post a 6-2, 6-1 victory over the fourth seed.

Unheralded American Mashona Washington compounded Russia's [Images] miserable day at the tournament with a 6-4, 4-6, 6-4 victory over eighth-seed Vera Zvonareva [Images].

Number 14 seed Daniela Hantuchova [Images] was the other seed to fall, losing 7-5, 4-6, 6-2 to doubles partner Ai Sugiyama of Japan [Images].

Playing her first match since beating Wimbledon [Images] champion Venus Williams [Images] in the final of the Stanford Classic on Sunday, the seventh seeded Clijsters was her normal consistent self.

"She hits the ball hard, flat and deep and it was just a matter of breaking her rhythm," said the 22-year-old Belgian. "I built my way into the match and kept bringing balls back until she made the mistakes.

"Whenever I get on hard courts, for whatever reason, I just feel good."

BREAKOUT YEAR

Playing with a right elbow strain, Petrova was unable to impose herself against Mirza, who dictated play during the match.

Mirza, who had to qualify for the main draw, was never threatened by the 2005 French Open semi-finalist, though the Indian said nothing was easy playing a top-10 ranked player.

"I knew if I relaxed for a second she would have jumped on me," said Mirza, who will face Japan's Akikio Morigami in the next round. "I had a game plan in my mind and I'm glad I was able to do what I needed to.

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"I believed I could do it, but I always knew that everyone is beatable."

Ranked a career high 59, Mirza is almost sure to crack the top 50 in the next two weeks, achieving the goal she had set herself at the beginning of the year.

She has already won her first career title, at Hyderabad beating four seeds on the way, beat the then world number seven Svetlana Kuznetsova [Images] in Dubai and made two other quarter-finals.

"A lot has happened since January," the 18-year-old added. "I started this season losing in the second round of qualifying of Tasmania.

"I didn't expect so much to happen so soon, but I'm not complaining."

PIERCE THROUGH

While fifth seed Patty Schnyder survived a 6-4, 6-7, 6-1 match against Czech Kveta Peschke, French Open finalist Mary Pierce, playing her first match on hard courts since March, thrashed Germany's [Images] Anna-Lena Groenefeld.

"I didn't expect to play that well because in your first match on a surface, you don't know what's going to happen," Pierce said of the 6-1, 6-1 victory.

"I was really happy today, especially with the first set. I took her seriously. From first point of match, I was ready to play."

In other matches, ninth-ranked Elena Likhovtseva recovered from a set down to beat Israel's Shahar Peer 0-6, 6-2, 6-4, while 10th seed Nathalie Dechy also came from a set down to beat Argentine Gisela Dulko 4-6, 7-5, 7-6.

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