Defending champion Juan Martin del Potro beat Marcos Baghdatis to reach the quarter-finals of the Swiss Indoors.
Del Potro won 6-1 6-2 in 72 minutes for his third win of the year over Cypriot Baghdatis and will next face Paul-Henri Mathieu.
"The start was tough for me," said Del Potro, who broke twice in each set and took victory on a fourth match point.
"I had a tough service game to start but then I gained confidence after I broke him for the first time.
"I served better than yesterday and generally played a better match. I led 5-0 in the first set but also had some easy mistakes. You have to be careful against a good player like him, he can come back at any time."
Mathieu saw off his fellow Frenchman Michael Llodra 6-4 6-3.
Dimitrov next for Federer
Also on Thursday, eighth seed Grigor Dimitrov extended his winning streak to eight matches with a 6-3 6-2 success against Ukraine's Alexandr Dolgopolov.
The Bulgarian's reward is a last-eight meeting with local hero Roger Federer, who has won the title in Basel five times but was beaten by Del Potro in last year's final.
Canadian Vasek Pospisil reached his third quarter-final of the season with a 6-3 6-4 defeat of Ivo Karlovic.
Frenchman Edouard Roger-Vasselin ousted German Tobias Kamke 7-5 6-3, while Daniel Brands of Germany defeated Poland's Lukasz Kubot 6-2 6-4.