Houston, TX (SportsNetwork.com) - Defending champion Fernando Verdasco and fifth-seeded Colombian Santiago Giraldo were opening-round winners Tuesday at the U.S. Men's Clay Court Championship.

Verdasco, seeded sixth, took the first set against Paolo Lorenzi 6-3 and was leading the second set 4-3 when his Italian opponent retired with an injury.

Giraldo drilled qualifier and fellow South American Rogerio Dutra Silva of Brazil 6-2, 6-2 at River Oaks Country Club.

Another seed moved on when No. 7 Jeremy Chardy of France handled Serb Dusan Lajovic 6-4, 6-4.

Meanwhile, an all-American affair saw two-time NCAA singles champion Steve Johnson defeat left-hander Donald Young 7-5, 6-4.

The home-court advantage didn't help Tim Smyczek, who was beaten 6-3, 6-3 by Russian Teymuraz Gabashvili.

Also advancing were American Jack Sock, Korean qualifier Hyeon Chung and Serbian wild card Janko Tipsarevic. Tipsarevic edged Brazilian qualifier in a third-set tiebreaker in his first singles match following an 18-month break. He underwent two surgeries to treat a fibromatosis in his left foot.