Osaka, Barty struggle but reach Melbourne quarters as Halep cruises

World number three Naomi Osaka and top-ranked Ashleigh Barty were pushed to the brink Wednesday, but both survived early exits at Melbourne Park, as Simona Halep cruised.

Japan's Osaka was made to work hard against in-form Katie Boulter, but fought back for a 3-6, 6-3, 6-1 victory to reach the quarter-finals in the Gippsland Trophy.

She next meets Irina-Camelia Begu from Romania as she ramps up preparations for the Australian Open starting Monday.

"Today was really tough for me. It just felt like a new experience playing here again after such a long while," Osaka said.

"For me, I thought she played really well. I sort of had to raise my level, kind of go within myself.

"I was actually more calm after losing the first set because I felt like for me, I just wanted to be able to play well," she added.

British world number 371 Boulter, who knocked out teenage sensation Coco Gauff Tuesday, ran her error-strewn opponent ragged to claim the first set in 39 minutes.

A refocused Osaka lifted her intensity to run away with the contest in a one-sided third set.

The three-time Grand Slam champion had comfortably beaten France's Alize Cornet in straight sets on Tuesday in her first competitive match since lifting her second US Open title in September.

World number one Barty also had a fright in her match against Marie Bouzkova of the Czech Republic, but recovered from a second-set stutter to win 6-0, 4-6, 6-3.

"Mid-match I lacked execution ... but happy to get it on my terms in the end," Barty said after a quick turnaround, having beaten Ana Bogdan in straight sets on Tuesday night.

Barty, hoping to break her country's 43-year singles title drought at the Australian Open, will face Shelby Rogers of the United States next.

Reigning Australian Open champion Sofia Kenin was also pushed hard by American Jessica Pegula, dropping the first set and finding herself 4-1 down in the second  before prevailing 5-7, 7-5, 6-2.

"I was happy the way I was able to change things in the second set ... I found my groove," Kenin said.

World number five Elina Svitolina also had to come from behind to beat 2017 French Open champion Jelena Ostapenko 6-7 (7/4), 6-3, 6-2.

She'll next face 20th-ranked Belgium's Elise Mertens, who knocked out Caroline Garcia of France 7-6 (7/1), 6-3.

World number two Halep bucked the trend and downed Laura Siegemund in straight sets to set up a Gippsland Trophy quarter-final against Russia's Ekaterina Alexandrova who upset French Open champion Iga Swiatek 6-4, 6-2.

"I'm really happy with both matches, so it's good to be back," said Halep who beat Anastasia Potapova easily on Monday.

Serena Williams is in action later Wednesday.