"I'm happy. Things are obviously pretty quick indoors," Federer said. "Thiemo can serve well and he is very talented, so it is a good victory for me."
The top-seeded Federer will face France's Julien Benneteau in the quarterfinals.
Second-seeded Juan Martin del Potro of Argentina also advanced, beating Latvia's Ernests Gulbis 7-6 (5), 6-3. Del Potro will play Finland's Jarkko Nieminen, a 6-3, 5-7, 6-3 winner over Germany's Matthias Bachinger.