Martina Hingis began her quest for a record fifth Pan Pacific Open title with a crushing 6-1, 7-5 win over Australia's Nicole Pratt on Wednesday.
The former world number one, a quarter-finalist at last week's Australian Open, needed only 66 minutes to reach the last eight with a clinical performance on the fast indoor carpet.
"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, who won the Tokyo title in 1997, 1999, 2000 and 2002.
"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."
Earlier, China's Zheng Jie, battling a high fever, overwhelmed American Bethanie Mattek 6-2, 6-1 to join compatriot Li Na in the last 16.
"I had a fever of 39c yesterday," the world number 33 told Reuters. "I'm not feeling very well. But I'm comfortable with my tennis and I'm enjoying every tournament now."
Zheng will play fourth-seeded Serb Jelena Jankovic in the second round of the $1.3 million tournament.
Sixth seed Li won her opening match in equally convincing fashion on Tuesday and plays Samantha Stosur next following the Australian's 6-4, 6-7, 6-4 win over Russia's Vera Zvonareva.
The winner of the Li-Stosur match faces Hingis in the quarter-finals.
Meanwhile, Russian Maria Kirilenko swept into the last 16 with a 6-2 6-3 upset win over seventh seed Shahar Peer of Israel.
Elena Likhovtseva beat Argentina's Gisela Dulko 6-3 6-2 to set up a second round meeting with fellow Russian and defending champion Elena Dementieva.
The world's current top-ranked player Maria Sharapova is scheduled to play her opening game on Thursday after reaching the final of the Australian Open at the weekend.
