Top seed Dinara Safina survived a tough test of her title credentials before beating Tsvetana Pironkova of Bulgaria 7-6, 6-2 in the second round of the WTA event in Indian Wells on Friday.
The Russian saved four set points in the first-set tie-break against a determined Pironkova before easing through the second set.
World number 50 Pironkova served for the first set at 5-4 but Safina broke straight back and then held her nerve in the tiebreak to win it 10-8.
The second was much more straightforward and Safina clinched victory to set up a third-round meeting with 28th seed Shahar Peer of Israel.
Fourth seed Vera Zvonareva, number eight Victoria Azarenka of Belarus and Danish ninth seed Caroline Wozniacki also advanced, as did former world number one Amelie Mauresmo.
But there was a shock defeat for sixth seed Sevtlana Kuznetsova as the former U.S. Open champion was beaten 6-2 4-6 6-3 by Urszula Radwanska of Poland in round two.
Both players led by a break of serve in the final set but Radwanska eventually got the crucial one in the eighth game and held on in a marathon final service game for victory.
Mauresmo, who won her first title in two years last month in Paris, battled past German Anna-Lena Groenefeld 5-7, 6-3 6-4 in three minutes short of three hours.
"It was not a great level of play, but the main thing was done today, to win and to go through this first match, which wasn't so easy," Mauresmo said.
"It's my first match after almost four weeks now. You want to try to get into it and get into a rhythm, which was not so great today.
"But it was a good fight, and I am just happy to go through and have the opportunity to do better for the next one."
In the men's event, German qualifier Michael Berrer beat South African Kevin Anderson 6-3, 6-3 and will meet world number one Rafa Nadal in the second round.
German Tommy Haas was among the day's other first-round winners.