Andy Murray won a seventh Masters title as world number one Novak Djokovic retired from the Cincinnati final with a shoulder injury at 6-4 3-0 down.
It was only the second loss of the year for the Wimbledon and Australian Open champion, who has won 57 times in 2011.
Djokovic recovered an early break to pull level in the opening set, but surrendered his serve straight after.
He received treatment between sets, but conceded defeat to hand Murray the title after netting a limp smash.
It was an underwhelming end to a match that had promised to be a more thorough test of Murray's US Open credentials.
The Scot progressed to his first Grand Slam final at Flushing Meadows in 2008, straight after winning his first Masters title against Djokovic in Cincinnati the previous month.
Hopes of a similar run for the British number one this year will have been raised by the fates of the three men above him in the world rankings in Ohio.
while Djokovic, who looked short of energy throughout the final, seems to be feeling the effects of his outstanding season.
The Serb offered up two break points to Murray in the first game of the final and slipped behind with a stray cross-court forehand.
He continued to fall short of his usual high standard and a framed forehand under little pressure was one of a string of unforced errors.
Murray landed with more than 70% of his first serves in an impressive start to the set, but Djokovic seemed to be back in the match when he overhauled the Scot in the sixth.
Confronted by a succession of deep groundstrokes onto his baseline, Murray could not find the required winners when challenged to seize the rally.
But he struck back immediately, winning an enthralling rally to take the second of two break points in the seventh and held his next two service games to consolidate and seal the set.
A court-side doctor set to work on the niggle to Djokovic's right shoulder during the interval, but the break seemed to drain rather than restore his energy.
He meekly gave up another break in the first game of the second set before Murray held to love with the only ace of the match.
Djokovic brought the contest to an early end when, with an open court in front of him, he patted a routine overhead into the net to slip a double-break behind.
"Obviously when he started to slow down his serve toward the end of the first set it was going to be tough for him," said Murray, who also won in Cincinnati in 2008.
"Sometimes things can warm up when you play, sometimes they get worse. I just tried to stay focused."