Top seed Caroline Wozniacki of Denmark on Tuesday lost her opening match of the season at the WTA Medibank International tennis tournament.
A day of rain interruptions did little to make life easier for the 20-year-old in the second-round match, which she lost to Dominika Cibulkova of Slovakia 3-6, 3-6.
Third seed Kim Clijsters continued to roll as she put out Czech Barbora Zahlavova Strycova 6-1, 6-4 while China's eighth seed Li Na beat Virginie Razzano of France 6-4, 1-6, 6-4.
Wozniacki, still looking for a first career Grand Slam title, has had a busy pre-season, playing energy-draining exhibitions in Thailand and Hong Kong before finally venturing onto court for a serious match more than a week into 2011.
She is now likely to head to Melbourne to try to quickly regain form with that city's Australian Open starting Monday.
"At the start of the new season, you always need to get into the match play," said Wozniacki, who has bettered the 32nd-ranked Cibulkova 5-1 in their career series.
"I didn't feel that I was playing great tennis out there.
"I just need to get some sets going and some training matches, head to Melbourne and get ready." She acknowledged her travel schedule was straining but refused to blame it for her performance.
Thomaz Belluci recovered from a mid-match slump to beat American qualifier Michael Russell 6-4, 6-7 (4), 7-5 in the first round of the Heineken Open tennis tournament. Belluci, ranked 31 and the No. 5 seed, led 6-4, 5-3 before wavering, dropping the second set and falling behind 3-0 in the third in a hard-hitting duel with the 103-ranked Russell.
The 32-year-old American then won seven straight games to capture the second set in a tiebreaker and to lead by two service breaks in the third.
Belluci had made 32 unforced errors by the third game of the final set but he then lifted his game, falling in behind the swinging left-handed serve which had been strong in the first set and at the start of the second.