Juan Martin del Potro of Argentina had 10 aces in defeating Brian Baker of the U.S. 7-5, 6-1 Thursday to advance to the Swiss Indoors quarterfinals.
Del Potro, seeded second, plays Kevin Anderson of South Africa in Friday's quarters. Anderson beat Marinko Matosevic of Australia 6-3, 6-7 (5), 6-3.
Top-seeded Roger Federer has a quarterfinal against Benoit Paire of France, who on Thursday downed Lukasz Kubot of Poland, 6-4, 6-4.
In other second-round matches, sixth-seeded Mikhail Youzhny of Russia beat Matthew Ebden of Australia, 6-3, 6-1, and Paul-Henri Mathieu of France ousted Nikolay Davydenko of Russia 6-3, 6-7 (2), 6-4.