Top seed Maria Sharapova overcame a slow start to beat Francesca Schiavone in her opening match at the Pan Pacific Open in Tokyo on Thursday.
Sharapova moved to the top of the world rankings this week
The Russian, who lost to Serena Williams in last Saturday's Australian Open final, saw off Italian Schiavone 7-5 2-6 6-1.
Sharapova will next play Ai Sugiyama, who beat Maria Kirilenko 3-6 6-1 6-3.
Other winners on Thursday included third seed Elena Dementieva and fourth seed Jelena Jankovic.
Dementieva beat fellow Elena Likhovtseva Russian 6-3 7-5, while Jankovic thrashed Jie Zheng 6-4 6-0.
Fifth seed Ana Ivanovic beat Mara Santangelo 4-6 6-1 6-2 and Samantha Stosur upset sixth seed Na Li 6-2 6-4.
I always find it tough to get into a rhythm in my first match here
Stosur goes on to face second seed Martina Hingis in the last eight.
Sharapova had clearly not got over her thrashing by Williams in Melbourne.
After twice fighting back from a break down to take the opening set against Schiavone, the world number one's game deserted her in the second.
With on-court coaching allowed in Tokyo, Michael Joyce told her: "It all goes back to your serve.
"You've just got to get it together and find a way to win."
The talking to worked as Sharapova stormed through the deciding set to secure a quarter-final place.
"He just told me to keep fighting," said Sharapova afterwards.
"I didn't play my best tennis in the second set or the first for that matter and he just told me to fight for every point."
She added: "I always find it tough to get into a rhythm in my first match here. It took longer than I wanted but I'm happy to get the win."