Japan's Naomi Osaka has beaten Dominika Cibulkova 6-2 6-1 at the Pan Pacific Open in Tokyo - her first match since winning the US Open.
The 20-year-old beat Serena Williams to win her first Grand Slam earlier this month - a victory overshadowed by Williams' outbursts at the umpire.
The third seed raced to victory in 59 minutes against Slovakia's Cibulkova.
She will play either Barbara Strycova of the Czech Republic or Estonia's Anett Kontaveit in the quarter-finals.
"I didn't really feel any pressure," said Osaka, the tournament's 2016 champion.
"It was really difficult because she's such a great player but I just thought it was more fun."