The prospect of playing five sets in stifling heat and humidity Thursday at the National Tennis Center was not an appetizing prospect for anyone, but after losing the first two sets to Frenchman Adrian Mannarino, it was either that for third-seeded Andy Murray or make his earliest Grand Slam exit since the 2008 Australian Open.

So, for the eighth time in his career, Murray not only fought back from that two-set hole but turned dominant over the final three sets to pull out a 5-7, 4-6, 6-1, 6-3, 6-1 victory to advance to the third round.

Sounding fatigued and fighting a head cold, Murray said he drew on his reservoir of experience. "I've come through many tough matches in my career, and I think when you've done it in the past, you have the belief that you can come through and do it again."

The Englishman blew a chance to take control early when he converted only one of seven break points in the opening set. In the second set, he only had one break point and missed it, too, as Mannarino positioned himself for a monumental upset.

But during the final three sets, Murray's consistency from the baseline and maybe the moment, too, proved too much for Mannarino. It wasn't as easy as the scores would suggest. Murray explained that he was leaning on his racket in the fourth set from sheer fatigue.

"It was extremely tough conditions, especially in the beginning of that fourth set, some unbelievable points kind of back-to-back with a lot of running," Murray said. "It was not an easy match to come through at all."

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Next for Murray is 30th-seeded Brazilian Thomaz Bellucci. On paper, Murray should breeze to the quarterfinals and a possible meeting with No. 5 Stan Wawrinka, who won a tense 7-6 (2), 7-6 (4), 7-6 (6) decision against 19-year-old South Korean Hyeon Chung. But the invisible enemy at an Open where 12 players on the men's side have been forced to retire is fatigue.

Asked if he might pay later for the five sets he played Thursday, Murray said, "In these conditions, obviously it can take its toll later on in the tournament. Thankfully, the last three sets were fairly comfortable in terms of score line, otherwise, I could have been out there much longer. It would have been very tough to recover from."

The rest of the tournament might turn into a case of survival of the fittest, and if that's the case, Wawrinka is confident. Asked what can be done about all the retirements, Wawrinka said, "We can be better physically maybe, first thing to do…I don't have problem physically. Never retired because of cramping."

Wawrinka was impressed with the youthful Chung but outdueled him in the tiebreakers to get out of the heat. "It could have been four, five sets," Wawrinka said. "He played some great tennis in those tiebreaks, and I'm glad to win this match."

In contrast to some of the other top seeds, No. 2 Roger Federer barely broke a sweat during his 6-1, 6-2, 6-1 victory over Belgian Steve Darcis. The all-time men's Grand Slam leader scoffed at all the retirements, saying, "Really no excuse for that. I think everybody should be well-prepared."

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No. 24 Australian Bernard Tomic defeated countryman Lleyton Hewitt, 6-3, 6-2, 3-6, 5-7, 7-5. It was the final U.S. Open for Hewitt, the 2001 champion, who will say farewell in January in Australia.