Beijing gold medallists Rafael Nadal and Elena Dementieva shook off their Olympic hangovers on Monday to stumble into the second round of the US Open.
As the newly-crowned world number one, Nadal would have been expected to flatten a qualifier ranked 136th in the world.
But the Spaniard's exertions over the past few weeks, where he made a flying visit to the Chinese capital to add the Games title to his triumphs at the French Open and Wimbledon, appeared to have caught up with him as he struggled to a 7-6, 6-3, 7-6 win over Germany's Bjorn Phau.
"The problem is playing Toronto, Cincinnati and Beijing, then coming back here. In two weeks, two times, 12 hours' jet lag," said Nadal, who ended Roger Federer's record run of 237 consecutive weeks at the top last Monday.
"I'm a little bit more tired than I usually am but, at the same time, I must be very happy how I did this year."
Dementieva, after finally getting her hands on a major title, also found it difficult to break free from the Olympic bubble.
She snapped back to attention in the nick of time to come from 5-3 down in the second set, saving two set points, before beating Akgul Amanmuradova of Uzhbekistan 6-4, 7-5.
Eight days after pulling off the greatest win of her career, Dementieva admitted she was still pinching herself.
"I was holding (the medal) for three days, to make sure it's not a dream. It's real," said the Russian fifth seed.
"It's really very hard not to think about the Olympic Games. Yesterday I was trying to go to sleep but I couldn't because... my mind is still there."
Phau must have also experienced a sleepless night at the prospect of facing the imposing figure of Nadal across the net.
But once he stepped on to the Arthur Ashe Stadium court, he put in a nerveless display to rattle the Spaniard.
Nadal eventually revealed his iron will to end Phau's brave challenge in just under three hours.
On a night when Flushing Meadows paid a glittering tribute to the players who have won singles titles in New York since tennis turned professional in 1968, Nadal and Dementieva led a parade of Olympic champions, past and present, into round two.
Lindsay Davenport, winner in Atlanta in 1996, did not seem to suffer from any ill effects from the knee injury which has curtailed her season and eased past Canada's Aleksandra Wozniak 6-4, 6-2.
Men's 10th seed Stanislas Wawrinka, who helped Roger Federer fulfil his Olympic dream by winning the doubles crown in Beijing, beat Simone Bolelli of Italy 7-6, 6-3, 6-3.
British sixth seed Andy Murray lived up to his billing as a title contender when he gave unlucky Argentine Sergio Roitman the run-around in a 6-3, 6-4, 6-0 mauling.
Roitman's compatriot David Nalbandian enjoyed better fortune and overcame Brazilian Marcos Daniel 6-1, 6-2, 6-4.
Second seed Jelena Jankovic underlined her title aspirations with an unforgiving 6-3, 6-1 exhibition against Grand Slam debutante Coco Vandeweghe.
On a low-key opening day for the season's final grand slam, third seed Svetlana Kuznetsova, former Wimbledon runner-up Marion Bartoli, 15th seed Patty Schnyder and men's fouth seed David Ferrer all advanced.
Tenth seed Anna Chakvetadze's challenge, however, stalled in the opening round. She collapsed to her earliest grand slam defeat in over three years when she was hustled out 1-6, 6-2, 6-3 by fellow Russian Ekaterina Makarova.