Martina Hingis began her campaign for a record fifth Pan Pacific Open title with victory over Australia's Nicole Pratt in Tokyo on Wednesday.
Hingis first won the title in 1997
The former world number one, who lost to Elena Dementieva in last year's final, came through 6-1 7-5.
"I beat her 6-0 6-1 in Gold Coast in my first tournament of the year so I was comfortable playing her," said Hingis.
"I'm trying to be more offensive and take the game into my own hands. I know that's the direction I have to take."
Hingis was broken when serving for the match at 5-4 in the second set but took the next two games to set up a a quarter-final against sixth seed Li Na or Stosur.
"This surface really suits my game," said Hingis. "If you can play offensively and come in every now and then it can really help you, and that's what I've done in the past."
Russia's Maria Kirilenko had an impressive 6-2 6-3 win over seventh seed Shahar Peer, while Samantha Stosur and Jie Zheng also progressed.
Top seed Maria Sharapova will play Francesca Schiavone on Thursday.