Former world number one Martina Hingis pulverised South Korea's Cho Yoon-Jeong 6-0, 6-0 in the Pan Pacific Open first round on Wednesday.
The Swiss returned to tennis last month and reached the Australian Open quarter-finals in her first Grand Slam since retiring through injury in 2002.
Hingis looked as though she had never been away, completely outclassing her Korean opponent in just 33 minutes.
A four-times Pan Pacific Open champion, Hingis will play third seed Nathalie Dechy of France in the last 16 of the $1.3 million (731,000 pound) tournament.
Earlier, second seed Elena Dementieva overcame an erratic start to beat Slovenia's Katarina Srebotnik 2-6, 6-1, 7-5 and reach the quarter-finals.
Dementieva had suffered a shock first-round exit at the Australian Open and the Russian was forced to work hard for her first victory of the year.
The world number nine will face Czech Nicole Vaidisova in the last eight after the fifth seed beat Japan's Saori Obata 6-4, 6-4.
Fifth seed Vaidisova plays Obata in a second-round match later on Wednesday.
Russian seventh seed Elena Likhovtseva overpowered Japan's Shinobu Asagoe 6-3, 6-2 in the first round.
In other matches, Lisa Raymond thrashed fellow American Meilen Tu 6-1, 6-3 to set up a second-round meeting with top seed and defending champion Maria Sharapova on Thursday.
Australia's Samantha Stosur breezed past Japan's Aiko Nakamura by the same score and next plays Slovakia's Daniela Hantuchova.
