Sixth-seeded Fernando Verdasco of Spain got a 7-6 (5), 6-2 victory over Steve Johnson of the United States in the U.S. Men's Clay Court championships on Tuesday.
Fifth-seeded John Isner, the second-ranking U.S. player, met Ryan Harrison in a later match.
Qualifier Robby Ginepri of the United States kept eighth-seeded Michael Russell of the United States off balance most of the match for a 6-2, 6-2 first-round victory.
Top-seeded Nicolas Almagro of Spain plays his first match Wednesday against Gael Monfils of France. Monfils, who missed most of last season with a knee strain, beat James Blake of the United States in the first round.
Verdasco won the tiebreaker when Johnson double-faulted at set point. Johnson held after four break points in the fourth game of the second set, but he was broken in the sixth and eighth games.
Ginepri broke Russell quickly in the first game of the match and again in the seventh game and wrapped up the first set in the eighth game aided by three Russell errors and he had an ace at the first set point.
Ginepri took control of the match in the opening game of the second set, breaking Russell at the fifth break point. Ginepri pounded in several down-the-line winners that left Russell flat-footed.