HOUSTON (AP) -- In a match representing one of the largest age gaps between players in recent decades on the men's tennis tour, 39-year-old Tommy Haas edged 19-year-old Reilly Opelka 7-6 (5), 4-6, 6-3 on Monday at the U.S. Men's Clay Court Championship.
It was the first ATP tour-level victory since Wimbledon in 2015 for Haas, once ranked as high as No. 2, but now semiretired and outside the top 800. Opelka is ranked 168th.
Haas earned his lone service break of the 6-foot-11 Opelka in the third set. Overall, Haas was 1 for 10 on break chances.
According to the ATP World Tour, the roughly 19½-year gap between Haas and Opelka ranks as the fifth-biggest in a tour match since 1995, and the eighth-biggest since 1985.
At night, defending champion Juan Monaco bowed out in the first round, losing to the higher-ranked Dustin Brown 7-6 (7), 6-3.
The 124th-ranked Monaco won the Houston title in 2012 and 2016. Brown is No. 75.
In another first-round match, Nicolas Kicker advanced when qualifier Noah Rubin retired while trailing 5-3 in the first set.