American Robby Ginepri moved easily into the Japan Open quarter-finals with a 6-4, 6-4 victory over Luxemburg's Gilles Muller on Thursday.
The third seed showed glimpses of the form that took him to the U.S. Open semi-finals last month, wrapping up victory in 70 minutes.
"I thought I returned extremely well, which helped me get into a lot of his service games, and that won the match," said Ginepri, who lost in five sets to Andre Agassi at the year's last grand slam.
"I don't feel as sharp as I did in the summer but that's going to change shortly."
Ginepri, who lost to British teenager Andy Murray in the quarter-finals in Bangkok last week, will play Germany's Bjorn Phau in the last eight. Phau thrashed 10th seed Kenneth Carlsen of Denmark 6-1, 6-2.
Second seed Radek Stepanek beat fellow Czech 7-5, 6-4 in a second round match, and American Taylor Dent, seeded fourth, overpowered Russia's Dmitry Tursunov 7-3, 7-6.
Top seed Mariano Puerta, who on Wednesday denied a report he had tested positive for a banned substance at this year's French Open, plays Marcos Baghdatis of Cyprus in the evening session.