GSTAAD, Switzerland, July 9 (UPI) -- Spain's Albert Costa, the top seed and reigning French Open champion, fell to a French qualifier Tuesday in the first round of the $600,000 Swiss Open claycourt event.
Playing in his first match since winning the world's top claycourt tournament, Costa was upset by the 20-year-old Paul-Henri Mathieu, 6-4, 6-3.
Mathieu, who reached the round of 16 at the French Open, in the second round will face Spain's Galo Blanco, who defeated Dutch qualifier Rogier Wassen, 7-5, 6-1.
Costa captured his first career Grand Slam title on June 9, winning the French Open with a four-set victory over fellow Spaniard Juan Carlos Ferrero.
Ferrero and Roger Federer of Switzerland, the second and third seeds, respectively, eased into the second round.
Ferrero rolled over compatriot Alberto Martin, 6-2, 6-2, and set up a second-round contest with another Spaniard, David Sanchez.
Federer posted a 6-4, 6-3 win over Hicham Arazi of Morocco. The Swiss No. 1 will take on Czech qualifier Radek Stepanek who beat Spaniard Francisco Clavet, 6-3, 6-3.
Only one other seeded player fell on Tuesday. No. 6 Nicolas Lapentti of Ecuador was eliminated by Attila Savolt of Hungary, 7-5, 1-6, 7-5. Savolt next faces Slovakia's Karol Kucera, who advanced on Monday.
No. 7 Gaston Gaudio of Argentina rallied to beat compatriot Franco Squillari, 2-6, 6-1, 6-4. Gaudio's next opponent is Mikhail Youzhny of Russia.
Austria's Stefan Koubek advanced with a 7-6 (7-2), 6-2 win over Argentine qualifier Nicolas Todero, and Marc Rosset defeated fellow Swiss wild card entrant George Bastl, 7-6 (7-5), 3-6, 6-3.
Koubek will meet Ivo Ljubicic of Croatia and Rosset awaits the winner of the first-round contest between No. 4 Andrei Pavel of Romania and Wimbledon finalist David Nalbandian.