Former champion Tomas Berdych advanced to the Japan Open quarterfinals with a 6-3, 7-5 victory over Alejandro Falla of Colombia on Thursday.
Berdych was joined by Janko Tipsarevic of Serbia, Milos Raonic of Canada and Marcos Baghdatis of Cyprus.
The third-seeded Tipsarevic beat Swiss qualifier Marco Chiudinelli 6-4, 6-2, while Baghdatis ousted fourth-seeded Juan Monaco of Argentina 7-5, 1-6, 6-3.
No. 6-seeded Raonic moved on when his second-round opponent, Viktor Troicki of Serbia, retired with a right calf injury while trailing 3-0.
Defending champion Andy Murray will take on seventh-seeded Stanislas Wawrinka of Switzerland in a quarterfinal on Friday, while Tipsarevic will meet Raonic in another.
Berdych broke Falla once in each set without giving away a break chance, and closed their first meeting with his ninth ace at Ariake Colosseum. He notched his 50th win of the season.
The Czech, the 2008 champion here, is seeking his second title of the year after winning indoors in Montpellier, France, in February.
"The big difference between today and my first-round match is that I am feeling much better physically," Berdych said.
Late Thursday, eighth-seeded Kei Nishikori of Japan took on Tommy Robredo of Spain.