HOUSTON, April 9 (UPI) -- Sixth-seeded German Benjamin Becker was a first-round upset loser Monday at the U.S. Men's Clay Court Championships in Houston.
Croat Ivo Karlovic defeated Becker in 7-5, 7-6 (7-3). The 6-foot-10 Karlovic had 16 aces and Becker broke his serve only once.
American Mardy Fish beat Austrian Jurgen Melzer in last year's final.
This week's top seeds are three-time Houston champion and two-time runner-up Andy Roddick, James Blake, 2004 winner Tommy Haas, Fish and Melzer.
Former world No. 1 Roddick will open this week against Spaniard Albert Montanes. Roddick, ranked third, reached five straight finals here before Haas beat him in last year's quarterfinals.