HOUSTON (AP) -- Sebastien Grosjean took advantage of Andre Agassi's serving troubles and snapped a string of seven straight losses to top 10 opponents with a 4-6, 6-1, 6-2 upset on Friday night in the quarterfinals of the U.S. Men's Clay Court Championships.
Top-seeded Andy Roddick powered his way into the semifinals earlier Friday, closing a 6-4, 6-1 win over Luis Horna with four straight aces.
In another quarterfinal, Jurgen Melzer eliminated defending champion Tommy Haas 2-6, 6-2, 6-4.
Melzer, in the tournament's final four for the second time in three years, will face Roddick in today's semifinals.
James Blake was to play qualifier Nicolas Lapentti later Friday in the last quarterfinal.
Agassi struggled in his long three-set victory over Alex Calatrava on Thursday and his problems caught up with him against the relentless Grosjean, who took charge early in the second set and never allowed the No. 2 seed to get back in the match.
Agassi hit 49 percent of his first serves for the match.
With the score at 1-1 in the second set, Agassi won only four more points the rest of the set as the sixth-seeded Grosjean broke Agassi in the fourth and sixth games and again in the opening game of the third set.
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