Sebastien Grosjean celebrates victory over Andre Agassi, Friday
French tennis star Sebastien Grosjean capitalized on American Andre Agassi's serving problems and pulled off the upset Friday night with a 4-6, 6-1, 6-2 victory in the quarterfinals of the U.S. Men's Clay Court Championships in Houston, Texas.

Second-seeded Agassi, who only hit 49 percent of his first serves, fell apart after winning the first set. The sixth-seeded Grosjean moves on to play Nicolas Lapentti of Ecuador in the semifinals. Lapentti got by American James Blake 6-4, 1-6, 7-6 in a battle of unseeded players.

Top-seeded Andy Roddick of the United States powered his way into the semifinals in a 6-4, 6-1 straight-set, victory over number eight Luis Horna of Peru. Roddick hit 14 aces and 70 percent of his first serves against Horna. Roddick will play seventh-seeded Austrian Jurgen Melzer, who ousted third seed and defending champion Tommy Haas of Germany, 2-6, 6-2, and 6-4.