Seventh-seeded Paolo Lorenzi overpowered Austrian qualifier Gerald Melzer 6-2 6-2 in the opening round of the ATP Tour’s US Clay Court championships in Houston on Tuesday.

The 31-year-old Italian Lorenzi blasted three aces and won 68 per cent of his first-serve points.

It was the first career match between world No.62 Lorenzi and the 22-year-old Melzer, who is the younger brother of Austrian star Jurgen Melzer. Jurgen was runner-up at Houston in 2006.

Lorenzi next faces countryman Flavio Cipolla, who beat Argentine qualifier Facundo Arguello 4-6 6-4 7-5.

In the night match, returning finalist John Isner engineered a 7-6 (7-4) 6-4 win over Ryan Harrison.

Isner finished runner-up to Argentine Juan Monaco last year in Houston.

In other matches on Tuesday, American Robby Ginepri notched his first tour-level win in more than a year as he rolled over eighth seed Michael Russell 6-2 6-2.

In another all-American first-round match, wildcard Jack Sock converted his two break point chances to beat qualifier Bradley Klahn 7-6 (7-3) 6-3.

Australia’s Lleyton Hewitt opens his campaign against Argentine Martin Alund in the first match on centre court on Wednesday while top-seeded Spaniard Nicolas Almagro will face Frenchman Gael Monfils.