Juan Monaco defeated John Isner 6-2, 3-6, 6-3 in the final match of the U.S. Clay Court Championship on Sunday.
Isner would've moved up to No. 8 in the rankings with a victory, but the Argentine broke Isner's serve three times to hand the American his first clay loss of the year.
Monaco won on clay for the second time this year and improved to 11-2 on the surface this year overall. He came in ranked 16th and his first victory in America will move up him to No. 14, matching a career high.
Isner won 44 consecutive service games in the tournament before Monaco broke him twice in the first set to take control. Isner had eight aces in the match, but also had five double faults.