Jack Sock made short work of former champion Ivo Karlovic, winning 6-1, 6-4 in the first round of the U.S. men's Clay Court Championship on Monday.
The 21-year-old American had lost both previous meetings with the 6-foot-10 (2.08-meter) Karlovic, who won the only U.S. men's tournament played on clay in 2007.
Sock broke the eighth-seeded Croatian's huge serve twice in the first set and wound up spending less than an hour on the court.
Germany's Dustin Brown also easily moved on, beating American Rhyne Williams 6-1, 6-2. Williams had reached the semifinals last year.