NEW YORK -- Before this U.S. Open, most tennis players played down the Beijing Effect.
Typically, they would shrug and say that they are citizens of the world and that travel -- even halfway around the world -- is nothing special.
But midway through the second week, as the unforced errors have mounted, the line at the trainers' table has lengthened and the word "exhausted" has begun to appear regularly in interview transcripts, it is clear that something is at work here.
Call it the China Syndrome.
On Tuesday, No. 3 seed Novak Djokovic was extended almost beyond his physical limits in a 3-hour, 44-minute, five-set victory over Tommy Robredo. No. 5 seed Nikolay Davydenko wasn't so lucky. He fell to qualifier Gilles Muller -- who did not journey to the Far East –- 6-4, 4-6, 6-3, 7-6 (10), a significant upset.
And then there was the case of Roger Federer. Seeded No. 2, Federer had won all nine of his previous sets, but Russia's Igor Andreev nearly took down the four-time defending champion. Federer prevailed 6-7 (5), 7-6 (5), 6-3, 3-6, 6-3. Some 3 hours and 32 minutes after the last match of the day session ended in prime time, at 8:23 p.m. ET, Federer turned to his box, pumped both his fists in unison -- and exulted.
Federer was uncommonly emotional during the entire match and almost giddy afterward. The tennis was, at times, thrilling. It was also ragged and sloppy. Federer finished with 67 winners and 60 unforced errors.
"Down a set and a tiebreak in the second, obviously there's danger written all over that situation," Federer noted. "It was really exciting, not only for the fans. I don't remember if I ever played a five-set match on that [Arthur Ashe] court. I don't usually give myself the opportunity.
"It's fun for a change"
"Honestly, going on the court I didn't expect that I'm going to win because I was just so exhausted," said Safina, who lost to Elena Dementieva in the gold-medal match. "I finish the warm-up and I just said, 'I cannot push myself anymore.'"
On the men's side, where they play best-of-five, instead of the women' best-of-three format, fatigue has played even more of a factor. A number of the men remaining in the tournament have been severely tested by lesser players on their journey to the quarterfinals.
"The Olympics maybe didn't help me right now for this tournament, no?" Nadal said. "Probably I am not in the freshest moment in my life."
Safe to say Federer was not at his freshest in the fifth set against Andreev. He fell into a hole, losing the first set in a tiebreaker, and could never seem to break free from the 25-year-old Russian, ranked 21 spots below him.
The match was consolidated when Federer, serving at 4-2, fought off four break points and escaped the six-deuce game when Andreev couldn't handle a fiery serve.
"I'm happy with the way I played when the pressure was the highest," Federer said.
Much was made of the choice by Roddick and fellow American Mardy Fish to skip the Olympics. Now that difficult decision looks prescient. Fish faces a depleted Nadal in one quarterfinal and if Roddick beats Gonzalez -- who reached the men's final in Beijing and played a tough match with Jarkko Nieminen -- he'll get Djokovic, who concedes that whoever he plays will be the fitter player.
In the end, Roddick is likely to experience his own version of the China Syndrome. After the Davis Cup semifinals in Spain, he is scheduled to play the China Open -- in Beijing.
Greg Garber is a senior writer for ESPN.com.