Gauff has 'things to improve' after season-opening win in Auckland
US Open champion Gauff prevailed 6-4, 6-2 in her first match of the season, while second-seed Elina Svitolina was also made to struggle before outlasting Caroline Wozniacki 6-4, 6-3 in a battle of the comeback mums.
In the second round, Svitolina will play another US Open winner Emma Raducanu who, in her first match since being sidelined by injury last April, outlasted Romanian Elena-Gabriela Ruse over a tense three sets.
World number three Gauff raced to a 4-0 lead over Liu, ranked 92 places lower, before the fluidity slipped from her game.
She double-faulted twice to drop her serve and the gap narrowed to 5-4 when Liu broke again.
But the 19-year-old recovered her composure to take the first set when a loose Liu forehand sailed out.
Gauff broke twice more from 3-2 in the second to move into the second-round meeting with 16-year-old Czech Brenda Fruhvirtova.
"I definitely needed to be tested and I feel like I played well today for my first match in a while," declared Gauff, who is defending the Auckland title she won 12 months ago.
"There's obviously things I can do to improve but I'm happy with the win," she said, looking ahead to the Australian Open, which begins on January 14th.
Svitolina and Wozniacki, who both returned to the circuit last year after maternity leave, battled for one hour and 45 minutes before Svitolina triumphed.
Former world number three Svitolina won the opening two games before Wozniacki fought back to lead 4-3.
But another break enabled the Ukrainian to take the first set 6-4.
Svitolina built a 4-1 lead in the second but Wozniacki refused to yield and won the next two games before the Ukrainian stretched away again.
"It was really special for me to get such a great win today against Caroline," said Svitolina, who took a year off to start a family while Wozniacki was away for nearly three years.
"She's a great player and I'm really glad she came back," added Svitolina.
Raducanu was troubled by Ruse's power play in a match in which there were 11 service breaks.
After Raducanu won the first set 6-3 and Ruse the second 6-4, the 21-year-old Briton led 5-2 in the third then dropped her serve twice before taking the decider 7-5.
The 21-year-old who had operations on both wrists and an ankle described her inconsistent performance as "a match of ups and downs" and said she was pleased just to be back on court.
"It's difficult after such a long hiatus. But I'm grateful to be healthy," she said.
"I'm grateful to be able to move my body and not be bedridden or in a wheelchair. So it's pretty amazing just to be out here and playing."
Petra Martic, the seventh seed from Croatia, recovered from a slow start in which she dropped her opening serve and the first set to beat last year's beaten finalist in Auckland, Rebeka Masarova of Spain, 3-6, 6-3, 6-3.
