( CNN ) -- Former World No.1 Caroline Wozniacki made a shaky start to the new WTA season with a shock defeat to Kazakhstan qualifier Ksenia Pervak in the first round of the Brisbane International Monday . The Dane finished her 2012 campaign in fine fettle with an 18-3 record after the U.S. Open , but Pervak showed her promise with a 2-6 6-3 7-6 win in two hours 48 minutes . Wozniacki , watched by her boyfriend , golf 's World No.1 Rory McIlroy , powered through the opening set in just 29 minutes , but Pervak hit back to level . The pair had gone to three sets in their previous two meetings , both won by Wozniacki , but this time the tables were turned . The eighth seed led 2-0 and 30-0 but Pervak broke back and was dominant in the tiebreak , winning it 7-1 for her first victory over a top ten player . `` It 's tough to lose 7-6 in the third -- it could have gone either way , but it did n't go my way today , '' Wozniacki told the official WTA website . `` I had a good off-season . I 've been working very hard . It 's just always tough to play your first match of the season , '' she added . Wozniacki will now head to Sydney to get in some match practice ahead of the Australian Open , while Russian-born Pervak goes into the second round at Brisbane for the first time in four attempts . The shocks did not stop there as home hope and seventh seed Sam Stosur was beaten in the night match by Swede Sofia Arvidsson , going down 7-6 7-5 . Fourth seed Angelique Kerber came through in three sets against Georgia 's Anna Tatishvili , while her fellow German Sabine Lisicki beat Czech Lucie Safarova 6-2 6-4 . Lisicki will play women 's top seed Victoria Azarenka Wednesday . Serena Williams is already into the second round with a straight sets win over Varvara Lepchenko . In the men 's ATP event , which is headed by Britain 's Andy Murray , Japanese fifth seed Kei Nishikori began his campaign with a straights sets 7-5 6-2 win over Australian Marinko Matosevic .
Serena Williams beaten in first round of Brisbane International . Ksenia Pervak of Brisbane wins three -6 6-3 7-6 in marathon match . Australian Sam Stosur also exits to Swede Sofia Arvidsson . Sofia Arvidsson already into first round .