California: Vera Zvonareva converted the only two service breaks of the match, enabling her to beat veteran qualifier Jill Craybas 6-4, 7-5 on Tuesday night to progress to the round of 16 at the Mercury Insurance Open.
The No.3-ranked and top-seeded Russian, playing her opening match, had more trouble than expected against the American, who had the benefit of two qualifying matches to get into the main draw, then a first-round match on Monday.
The pair were on serve in the first set when Zvonareva broke to take a 5-4 lead. Craybas, ranked No. 125, wasted two break points in the next game before dropping the set with a backhand into the net.
Zvonareva broke late in the second set to take a 6-5 lead and served out for the win. Zvonareva's next opponent will be either No.16 seed Polona Hercog of Slovenia or Russian compatriot Vera Dushevina.
In the other second-round match, third-seeded Agnieszka Radwanska of Poland cruised early then fought off Britain's Elena Baltacha 6-0, 7-6 (4). Radwanska, who also received a bye into the second round, saved two set points at 5-4 in the second set before Baltacha saved one match point to force the tiebreaker.
In the round-of-16 the Pole will face either American Christina McHale or Russian Alla Kudryatseva, who beat No.13-seeded Jarmila Gajdosova of Australia.
Gajdosova was one of three seeded players to be bundled out in first-round matches: qualifier Marina Erakovic of New Zealand upset No. 14 seed Elena Vesnina of Russia 6-1, 6-2 and Alberta Brianti was a 1-6, 6-2, 6-2 winner over 10th-seeded Italian compatriot Flavia Pennetta.
No. 11 seed Maria Kirilenko of Russia cruised to a 6-3, 6-2 win over Canada's Rebecca Marino; 12th-seeded Sabine Lisicki of Germany beat Italian Greta Arn 6-0, 6-2; and No. 15 seed Sara Errani of Italy defeated Sania Mirza of India 6-2, 6-3.
Radwanska, runner-up in the finals here last year to Svetlana Kuznetsova, was in quite a struggle after an easy first set.
"I was serving very aggressively really playing my game," Radwanska said. "She was serving much better in the second set and it was hard to break her."
Kirilenko did not face a break point on her serve as she hit 75 percent of her first serves. She also took advantage of a back injury Marino suffered in the first set.
Kirilenko, who lost to eventual champion Serena Williams in the quarterfinals last week at Stanford, was rarely pushed by her Canadian opponent.
"I played great today," Kirilenko said. "I did everything that we planned. I was happy with that. I tried to mix my game because she is tall."
Both players sought injury treatment at the end of the first set. The Russian saw a trainer for a pain in her left leg, Marino for a lower back injury.
"I did a couple of drop shots and I could see that she was running a little bit (slower)," Kirilenko said.
Lisicki, who lost to Maria Sharapova in the Wimbledon semifinals, was pleased with her overall game.
"I didn't have too much time to adapt because I just came here two days ago," she said. "A little bit different conditions (than last week at Stanford), so I was happy with the way I played."