Andy Murray today stormed off the court after suffering an embarrassing first-round Olympic defeat to Yen-Hsun Lu of Chinese Taipei. The Scot had been one of the leading medal contenders for the men's singles but failed to master the humid conditions here and was beaten in straight sets 7-6, 6-4.

After being broken to 15 in the final game off the match, a furious Murray rushed straight for the changing room, choosing not to wait to leave the court with his ecstatic opponent. Cincinnati Masters winner Murray, who is the world No6, had looked to be cruising to a comfortable win during the first set.

However, he twice blew break advantages against the world No77, who has not progressed beyond the quarter-finals of an ATP tour event this season. Murray initially led 4-2 and 5-3, only to be broken back immediately each time as Lu showed more accuracy and purpose with his groundstrokes.

Murray fought back from 6-2 down in the tie-break to 6-5 only to double-fault and hand his opponent the set.

Growing in confidence, Lu held serve in the opening game of the second set then broke Murray when he flailed an awful backhand well wide of the tramlines.

It appeared to be better news for the Scot after a brief rain delay. He broke back immediately and then held serve in a marathon fourth game of the second set. Yet, he never looked in control, particularly on second serve which Lu regularly returned with ferocious pace.

Trailing 5-4, Murray was immediately put under pressure as he served to stay in the match. A stunning forehand crosscourt pass from Lu set up 15-40 and he converted a famous victory when the Scot netted a deep forehand approach.

Murray will be now be desperate to bounce back from this blow with a big performance in this month's US Open before he teams up with brother Jamie for a doubles match later tonight.

Elsewhere, Roger Federer cruised into the second round with a 6-4 6-2 victory over Russia's Dmitry Tursunov but his great rival Rafael Nadal made heavy weather of his match with Italian Potito Starace. The Wimbledon and French Open champion required three sets to complete a 6-2, 3-6, 6-2 success.

"I had a lot of opportunities. I didn't convert, so that was tough," Nadal said. "He had more problems than me when he was serving, so that gave me confidence."

Nadal now faces Australia's Lleyton Hewitt, a 7-5, 7-6 winner over Jonas Bjorkman of Sweden.