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.