Seventh-seeded Gael Monfils of France extended his successful return after several months out with a knee injury on Thursday, reaching the quarterfinals of the Moselle Open with a 7-6 (4), 7-5 victory over compatriot Nicolas Mahut.
It was Monfils' second match since losing to Brian Baker of the United States at the Open de Nice in May. The 2009 Metz champion hit 12 aces to secure a match against second-seeded Philipp Kohlschreiber.
''The fatigue builds up, I have lots of little niggles,'' Monfils said. ''I still feel a bit heavy, so I push and grimace a bit. But day after day, I'm getting better.''
Kohlschreiber, a runner-up three years ago, defeated Benoit Paire of France 6-2, 1-6, 6-1.
Third-seeded Marcel Granollers of Spain was forced to retire with an abdominal injury while trailing Ivo Karlovic 6-2, 2-2. The Croatian will face Nikolay Davydenko in the quarterfinals after the eighth-seeded Russian defeated Gilles Muller of Luxembourg, 7-5, 6-4.
Fifth-seeded Andreas Seppi of Italy also advanced, cruising to a 6-2, 6-1 victory over Frenchman Vincent Millot in just over an hour.
American Jesse Levine faces a quarterfinal match against top-seeded Jo-Wilfried Tsonga after beating Michael Berrer of Germany 6-3, 3-6, 6-0.