Ex-champions Sam Stosur and Caroline Wozniacki overpowered their unseeded opponents Wednesday to reach the third round of the WTA Tour\'s Family Circle Cup. The second-seeded Wozniacki breezed past Spaniard Silvia Soler-Espinosa 6-1, 6-1 just under an hour, while the third-seeded Aussie Stosur routed New Zealand\'s Marina Erakovic 6-1, 6-2 on the green clay at Daniel Island Tennis Center. Wozniacki, who won here two years ago, only entered the tournament on the weekend after she and golfer boyfriend Rory McIlroy postponed a trip to Haiti. Stosur won here in 2010 while Wozniacki claimed the title in 2011. \"I felt like I really served well and returned well today,\" Wozniacki said. \"I\'m pleased with that.\" Meanwhile, American qualifier Mallory Burdette surprised 15th-seeded 2009 champion Sabine Lisicki 3-6, 7-6 (7-5), 7-5 in their second round match. Burdette advances to the third round where she will face world number one and reigning Charleston champ Serena Williams. Also, No. 10 Julia Goerges of Germany held off Belarusian Olga Govortsova 6-2, 0-6, 6-3 and Canadian qualifier Eugenie Bouchard defeated No. 16 Brit Laura Robson 6-4, 3-6, 6-1. Bouchard will square off against Stosur next. American Madison Keys eased into the round of 16 with a 6-4, 6-3 victory over qualifier compatriot Grace Min. Keys will battle wild card Bethanie Mattek-Sands on Thursday. Taking the court later on Wednesday is fifth seeded Venus Williams, who squares off against Monica Puig. From: AFP