Cincinnati: Andy Roddick needed three sets to beat 46th-ranked Ukrainian Sergiy Stakhovsky 6-4, 6-7 6-1, while fellow American Taylor Dent upset Feliciano Lopez to advance to the second round of the Cincinnati Masters.
Roddick, who has struggled for form and fitness in recent weeks, produced some powerful serves but had to stay alert against an opponent who played some enterprising if erratic tennis.
The Ukrainian came out on top in the tiebreak at the end of a very tight second set but Roddick broke early in the third to take a firm grip on the match.
Dent, who last won an ATP tournament in 2003, beat Spaniard Lopez 6-3, 6-2 in perfect conditions on center court to set up a second-round clash with world number one Rafa Nadal.
Switzerland`s Stanislas Wawrinka comfortably defeated Spaniard Nicolas Almagro 6-3, 6-3 and will play the winner of the all-French match between Michael Llodra and Julien Benneteau.
Sam Querrey completed a good day for the United States by beating German Phillipp Petzschner 6-1, 6-4.