Garbine Muguruza staged a deciding-set fightback to defeat Sam Stosur and advance to the second round of the Brisbane International.
The French Open champion found herself 4-2 behind in the final set, but won five of the next six games to book a meeting with Daria Kasatkina thanks to a 7-5 6-7 (2-7) 7-5 victory.
The Spaniard enjoyed a breakthrough year in 2016, claiming her maiden grand slam title with a run to glory at Roland Garros, but she was slow to get going in her first outing of 2017.
Muguruza staved off three set points on her own serve at 5-4 down in the first set before breaking immediately and then holding to take the lead.
Stosur took the second on a tie-break to level and looked in good shape in the third, but Muguruza found her best form at a critical time to progress.
Ashleigh Barty made light work of Aleksandra Krunic, prevailing 6-2 6-2 to set up a clash with top seed Angelique Kerber.
"It's so exciting for me to get a crack at the world number one. It's the perfect way to start the season," said Barty, ranked 271st in the world.
Seeds Svetlana Kuznetsova, Elina Svitolina and Roberta Vinci all enjoyed safe passage on Monday while there were also wins for Shuai Zhang and Asia Muhammad.
Destanee Aiava was 3-0 40-15 up in her final set with Bethanie Mattek-Sands before inclement weather brought a halt, with the pair to resume on Tuesday.