CHARLESTON, SC, USA - It was a good day for the top seed, as Caroline Wozniacki recovered from an early first set deficit and eventually cruised past Barbora Zahlavova Strycova in her first match of the tournament, 64 61.

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Wozniacki, ranked No.2 in the world and the on-paper favorite for the Premier-level title here in Charleston, lost her serve in the third game of the match and found herself trailing 4-2; but she bounced back immediately with six straight games and ended up with a routine 64 61 victory over the feisty Czech player.

"I think I've transitioned well into the clay court season," said Wozniacki, now 6-0 on clay this year, having won five matches to defend her Ponte Vedra Beach title last week. "I feel comfortable on the clay. I can run forever, so it's the opponent who really has to think about finishing the points when they play me."

Next for Wozniacki is No.16 seed Patty Schnyder, who beat another teen-aged Sony Ericsson WTA Tour star earlier on, Michelle Larcher de Brito, 63 61.

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"Patty is a very experienced player. She has played lots of matches and has been around for a long time, so it won't be easy," said Wozniacki who has won two of her three previous meetings against Schnyder, including a first round win in Ponte Vedra Beach last week. "I played Patty last week, but tomorrow will be a totally different match and I'm going to go out there and enjoy myself."

Victoria Azarenka, the No.3 seed, wasn't so fortunate. Having won the first set, 6-2, she had to retire from her match against young American qualifier Christina McHale at 2-all in the second set due to a left thigh injury.

"I have a pulled hamstring," said Azarenka, who also retired from her quarterfinal match in Marbella, Spain last week because of the same injury. "I was hoping it would be better here, but it wasn't today. I just need to keep rehabbing it. It just kept getting worse during the match, so there was no point in playing more."

Other players reaching the last 16 included No.6 seed Nadia Petrova, No.8 seed Daniela Hantuchova, No.9 seed Alona Bondarenko and No.10 seed Elena Vesnina. Bondarenko saved three match points to beat Bethanie Mattek-Sands, 46 75 75, two at 4-5 in the second and one at 4-5 in the third.