Chardy swept by Mayer 6-3, 6-1 in 58 minutes. Half the games he lost were dropped serves but he ended up winning 61 percent of the points in the match. He piled up six breaks over Mayer's eight service games.
Also Thursday, seventh-seeded Albert Ramos stopped Victor Hanescu 6-2, 6-4 by finishing off three of his four break-point chances.
The win earned Ramos a quarterfinals shot against Chardy.
Thursday's other scheduled matches were postponed because of rain. That includes third-seeded Pablo Andujar going against Potito Starace in a rematch of last year's Grand Prix Hassan II championship match. Andujar won that match in straight sets.
The other postponed match featured qualifiers Lamine Ouahab and Sergio Gutierrez-Ferrol.