Serena Williams was a comfortable winner in her first singles match since the US Open final.
The 23-time grand slam singles champion took the rest of the season off after losing to Bianca Andreescu in New York but there was not too much rust evident in a 6-3 6-2 victory over Italy's Camila Giorgi at the ASB Classic in Auckland.
Williams, who also played doubles with Caroline Wozniacki on Monday, is happy with her start to the campaign.
She said on wtatennis.com: "(I) spent a long time off from tournament play, match play, so solid is pretty good. It's a great start to build on."
Top seed Williams next faces fellow American Christina McHale and could meet teenage prodigy Coco Gauff in the quarter-finals.
Wozniacki is playing the final month of her career having announced her intention to retire after the Australian Open, and she wasted little time easing to a 6-1 6-0 victory over local wild card Paige Mary Hourigan.
Defending champion Julia Goerges beat Greet Minnen 6-1 7-6 (4) while second seed Petra Martic and third seed Amanda Anisimova also reached round two.
At the Brisbane International, Australian Open champion Naomi Osaka had a tough start to her season under new coach Wim Fissette but battled to a 6-2 6-7 (4) 6-3 victory over Greek Maria Sakkari.
Maria Sharapova was edged out by American Jennifer Brady, though, the Russian winning the opening set but going down 3-6 6-1 7-6 (3) after two hours and 14 minutes.
Fifth seed Petra Kvitova lost the opening set to Anastasia Pavlyuchenkova but was dominant thereafter in a 2-6 6-1 6-0 victory while sixth seed Kiki Bertens beat Dayana Yastremska 6-4 1-6 6-3.
Madison Keys eased to a 6-3 6-2 triumph against Marie Bouzkova but Sloane Stephens was beaten 6-4 2-6 6-3 by Russian qualifier Liudmila Samsonova.
At the Shenzhen Open, defending champion Aryna Sabalenka and top seed Belinda Bencic were both knocked out.
Bencic lost her first-round encounter with Anna Blinkova 3-6 6-3 6-3 while Sabalenka was beaten 6-4 6-4 by Kristyna Pliskova.
It was a bad day for China, with eighth seed Zhang Shuai losing 7-6 (8) 6-3 to Kateryna Bondarenko while Wang Xiyu, Wang Yafan and Duan Yingying also lost.