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.