Frenchman Gael Monfils defeated compatriot Paul-Henri Mathieu to advance to the second round of the Mercedes Cup in Stuttgart.
Monfils had 16 aces in a 7-6 6-4 victory to set up a meeting with sixth-seed Florian Mayer, who defeated another German, Andreas Beck, 6-4 3-6 6-1.
There was no luck for British qualifier Alex Ward, who went down 7-6 6-3 to fifth seed Fabio Fognini.
The 23-year-old reached the main draw of the ATP Tour event by beating Ivo Minar in straight sets, but he could not repeat the feat against Fognini.
Ward hit four aces past his Italian opponent but, after surrendering a crucial break point in the first set, a lack of consistency on his serve through the second set ultimately saw him come undone in a tense tie-break.
Fognini will next play Argentina's Leonardo Mayer, who beat Pablo Andujar of Spain 3-6 7-6 7-6.
German Nils Langer had better luck as a qualifier, beating wild card Robin Kern 3-6 6-4 6-3 to set up a meeting with second seed Philipp Kohlschreiber, while Benoit Paire of France awaits Nikolay Davydenko, who beat Daniel Munoz De La Nava 6-7 6-3 6-4 in two hours and 25 minutes.