AUCKLAND, Jan 1, 2025 (BSS/AFP) - Four-time major champion Naomi Osaka used a rain break to her advantage to power to a straight-sets win in the second round of the Auckland Classic on Wednesday.

The Japanese star shook off some early mistakes to beat unseeded Austrian Julia Grabher 7-5, 6-3 and book a place in Friday's quarter-finals at the Australian Open warm-up tournament.

The first set went with serve to 5-5 before rain forced the players off court for just over an hour, allowing Osaka a chance to address a "nervous" start.

She consulted coach Patrick Mouratoglou, the former mentor of Serena Williams.

"I got some great advice from a great coach," Osaka, a former world number one, said.

"I just tried to focus on my bullet points and go out swinging if I had to go out, but thankfully I'm here to play another round."

The 27-year-old emerged to break late in the first set and early in the second to take control of the match in cool, windy conditions.

Osaka's serving was her strength, landing five aces and winning more than 80 percent of her points on second serve.

While the world number 57 wasn't broken, she struggled with her return of serve against Grabher, particularly in the first set.

"She was a really tough opponent to play against," Osaka said.

"I just felt I had to concentrate on myself a lot and try not to be as nervous as I felt."

Osaka has battled for consistency since returning to the court a year ago after the birth of daughter Shai in July 2023.

She said in the lead-up to Auckland that she was confident of revisiting her former glories.

Osaka climbed to world number one in early 2019 after winning the first of her two Australian Open titles.

The first Grand Slam of the year starts on January 12.