Brisbane - Japanese star Naomi Osaka came from a break down in the third set to overcome Greece's Maria Sakkari in the first round of the WTA Brisbane International on Tuesday.
Sakkari sniffed an upset when she won the second set in a tiebreak then broke Osaka's opening service game of the third set, but the former world number one dug deep and won 6-2, 6-7 (4/7), 6-3 in a two-hour opening-round clash.
Osaka, the tournament's third seed, said she was pleased with her first match of the year, after she was forced out of the WTA Finals in October with a shoulder injury.
"I'm really happy with how I served - I had to retire from my last match because of my shoulder thing, so I wasn't really sure how I was going to serve today," she said.
"But I was told I hit 16 aces, so that's pretty good for me."
Two-time Wimbledon champion Petra Kvitova came back from a poor first set to defeat Russia's Anastasia Pavlyuchenkova 2-6, 6-1, 6-0, while American qualifier Jennifer Brady downed Russia's Maria Sharapova.
Sharapova, a former world number one, was granted a wildcard into the event but although winning the first set, she eventually succumbed 3-6, 6-1, 7-6 (7/3).
Sixth-seeded Dutchwoman Kiki Bertens also progressed in three sets, beating Ukraine's Dayana Yastremska 6-4, 1-6, 6-3.
Eighth seed Madison Keys served brilliantly in her impressive 6-3, 6-2 win over Czech qualifier Marie Bouzkova.
The American made 70 percent of her first serves as she eased to a comfortable victory in just 66 minutes.
"I think it (my serve) was just working pretty well today," she said.
"I probably took a little bit of pace off but more just because I felt like I was kind of feeling my slider a little bit more.
"It's always nice when you can not only make your first serve, but it feels like it sets up the point really well for you."
Russian qualifier Liudmila Samsonova caused an upset when she beat former US Open champion Sloane Stephens.
Samsonova, playing only her seventh main draw WTA tournament, recorded her first victory over a top-30 player with her 6-4, 2-6, 6-3 win.
In other matches, Yulia Putinseva of Kazakhstan beat Croatia's Donna Vekic 6-3, 3-6, 7-5 and Estonian Anett Kontaveit overpowered Taiwan's Hsieh Su-Wei 6-4, 6-1.
Results from matches played on the second day of the WTA Brisbane International at the Queensland Tennis Centre on Tuesday (x denotes seed):
Madison Keys (USA x8) bt Marie Bouzkova (CZE) 6-3, 6-2
Liudmila Samsonova (RUS) bt Sloane Stephens (USA) 6-4, 2-6, 6-3
Yulia Putintseva (KAZ) bt Donna Vekic (CRO) 6-3, 3-6, 7-5
Naomi Osaka (JPN x3) bt Maria Sakkari (GRE) 6-2, 6-7 (4/7), 6-3
Anett Kontaveit (EST) bt Hsieh Su-Wei (TPE) 6-4, 6-1
Kiki Bertens (NED x6) bt Dayana Yastremska (UKR) 6-4, 1-6, 6-3
Petra Kvitova (CZE X5) bt Anastasia Pavlyuchenkova (RUS) 2-6, 6-1, 6-0
Jennifer Brady (USA) bt Maria Sharapova (RUS) 3-6, 6-1, 7-6 (7/3)