Defending champion Johanna Konta was beaten in the first round of the Sydney International, less than a week before the start of the Australian Open.
The British number one lost 6-3 7-5 to Agnieszka Radwanska in a repeat of last year's final.
World number nine Konta, 26, had retired from her last tournament in Brisbane because of a hip injury.
"I felt I recovered a lot quicker than I anticipated, which is a massively positive thing," she told BBC Sport.
"I think I'm right where I should be, coming off the end of last year. I'm happy again with the different kind of players that I've played so I feel good going into Melbourne - as good as I can feel."
Konta is set to be seeded 10th for the opening Grand Slam of 2018, which begins on 15 January.
Neither she nor former world number two Radwanska were able to dominate with their serve in the first set, with Konta in particular struggling on her second serve as her Polish opponent converted three of her five break opportunities.
Konta again had trouble holding serve in the second set but showed signs of a fightback when she broke while trailing 4-1 in the second, but was unable to build as Radwanska sealed victory in one hour and 49 minutes.
Radwanska, now down to 28th in the world having been hampered by injury last year, will face American qualifier Catherine Bellis in the second round.
Also through to the second round is Angelique Kerber who came from a set down beat second seed Venus Williams 5-7 6-3 6-1.
Former world number one Kerber is now ranked 22nd after a disappointing run of form in 2017 but she showed signs of resurgence against the American.
Williams, who was playing in the Sydney tournament for the first time since 1999, finished the first set strongly, coming from 5-3 down to win four consecutive games.
But, playing in her first match of the season, her accuracy deserted her at times in the second set and Kerber capitalised and went on to show her strength in the decider.
BBC tennis correspondent Russell Fuller
Konta made a bright start - moving, bending and stretching well - but lost her way against the crafty 2012 Wimbledon finalist. It was a horrid first-round draw.
Radwanska's stout defence and lack of pace caused many problems for Konta, who missed far too frequently from the baseline.
The Pole won seven games in a row at one stage, and had a double-break advantage in the second set. Konta rallied well, but could not quite extend the match into a decider.
There will be a subsequent loss of ranking points for Konta, but of greater importance was the speed of her recovery from the hip injury.