Houston - Marcel Granollers upset Taylor Fritz 6-2, 4-6, 6-2 in the first round of the US Men's Clay Court Championship on Monday.
Granollers, who won the title in 2008, beat No 5 seed Fritz, who reached the semi-finals last season, for his second tour-level victory this season.
Ryan Harrison beat 40-year-old Ivo Karlovic, who won the title in 2007, 6-3, 6-4.
Casper Ruud defeated Hugo Dellien 7-6 (9/7), 6-4, Christian Garin beat Pablo Cuevas 4-6, 6-4, 6-2 and Bernard Tomic defeated Denis Kudla 7-6 (10/8), 7-5 in the rest of the first-round singles action.
In doubles play, Austin Krajicek and Artem Sitak defeated Lleyton Hewitt and Jordan Thompson 6-2, 4-6, 10-8.
Play continues on Tuesday.