Former world number one Caroline Wozniacki opened her season with a win over German Julia Goerges in the first round of the Sydney International on Monday.
Danish sixth seed Wozniacki, who became engaged to golf star Rory McIlroy on New Year's Eve, lost the first set to Goerges but rallied to come through 3-6, 6-2, 6-4.
The 23-year-old, who withdrew from a WTA event in Brisbane last weekend due to a shoulder injury, was making her sixth straight appearance at the Sydney tournament as she prepares for the Australian Open.
But fourth-seeded Serb Jelena Jankovic's preparations for Melbourne hit a hurdle on Monday when she was beaten by world number 23 Ekaterina Makarova in straight sets, 6-4, 6-2.
Jankovic, who is ranked eighth in the world, was 3-1 down in the second set and was never back in the game as Makarova held her nerve to serve out for the match, winning with an ace.
"I tried to be aggressive and not let her attack, because she's really good playing down the line from the backhand," Makarova said.
"So I tried to let her move her to the backhand, not to stand and hit it. I was moving quite good (too)... today was a good match."
Earlier United States qualifier Bethanie Mattek-Sands beat Canada's Eugenie Bouchard 6-4, 6-3 while Czech Lucie Safarova bundled out Italian Francesca Schiavone 6-4, 6-4.
Mattek-Sands will now face defending champion Agnieszka Radwanska who, fresh from the final of the Hopman Cup in Perth, said she was expecting a tough match.
"I think Bethanie is playing well. I definitely have to play good tennis," she said.
Radwanska, the top-seed at the Sydney International and world number 5, played a thrilling final for Poland at the Hopman Cup with Grzegorz Panfil on Saturday, but lost to France's Jo-Wilfried Tsonga and Alize Cornet.
But Cornet could not continue her run on Monday and lost to American Christina McHale who took the match 6-7 (4/7), 6-2, 7-5.
German fifth seed Angelique Kerber beat last year's runner-up Slovakia's Dominika Cibulkova 7-6 (7/5), 7-5 while qualifier Lauren Davis from the United States took on Australian wildcard Jarmila Gajdosova, winning 6-4, 7-6 (10/8).
Romania's Sorana Cirstea went down to Bulgarian Tsvetana Pironkova 6-4, 6-1 and American Victoria Duval lost to Kaia Kanepi from Estonia 6-1, 6-3.
Fellow American Varvara Lepchenko -- a late edition after the US's Sloane Stephens pulled out with injury -- beat Russian Svetlana Kuznetsova 6-3, 3-6, 7-5.
In the men's singles, French sixth seed Julien Benneteau beat Australian Matthew Ebden 6-2, 6-2 and Uzbekistan's Denis Istomin won over Spaniard Pablo Andujar 6-1, 6-2.