Andy Murray has been hit by the tough conditions at the US Open and fears that being dragged into a five-set match with Adrian Mannarino in the second round might complicate his quest for a third Grand Slam title.
The world No.3 fought back from two sets down for the eighth time in his career against Frenchman Mannarino, whose unorthodox game kept him on the run on another sweltering day at Flushing Meadows.
Murray, the 2012 champion, finished strongly in wrapping up a 5-7, 4-6, 6-1, 6-3, 6-1 victory, but it took 3 hours 17 minutes and he revealed he has found the heat and humidity extremely tough as he battled a problem that has affected a number of other players, including brother Jamie.
Sounding hoarse in his press conference, Murray was asked if he was unwell. "A little bit, yeah," he said, adding that the illness had affected him "at the beginning of the match a little bit. But after the first couple games, [I] feel fine really. Quite a few of the players have had head colds. My brother was quite sick yesterday, as well. I think there's a few of the players have had it."
Murray has not lost to a left-handed opponent in 2015 -- he is now 11-0 as he prepares to face another leftie, Brazil's Thomaz Bellucci, in the third round. His recovery ahead of Saturday's match will be crucial after being made to work hard by world No. 35 Mannarino.
At times Murray sank to his knees and leaned on his racket between points, but the Scot insisted that he coped relatively well with the problems he faced.
"I was out of breath," Murray said. "I was bending over because I was tired. Normally after extremely long rallies you do that. 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.
"Yeah, I was tired. I wasn't holding myself up with my racket. I was just bending over. That's what I think a lot of people do when they're out of breath or tired.
"Normally the next day is when you feel it, when you wake up -- stiff and sore. I'll have a massage, come in and try and practice a bit earlier [Friday] so that I can get back and have a bit more time to maybe have a sleep in the afternoon tomorrow, spend as much time recovering as I can."
Murray praised Mannarino for playing "some really, really good tennis" and admitted the match had the potential to unsettle his preparations for the sharp end of the tournament.
"In these conditions, obviously it can take its toll later on," Murray admitted. "But unfortunately you don't always have the luxury of winning matches in straight sets. Sometimes you have to fight through. Maybe if you're not playing your best, just find a way to get through.
"Thankfully the last three sets were fairly comfortable in terms of scoreline; otherwise I could have been out there much longer - would have been, you know, very tough to recover from.
"I've played matches much longer than that. But, yeah, it's not easy to recover in these conditions."
Bellucci, whose four ATP titles have all come on clay, is through to the third round of the US Open for the first time in his career. The No.30 seed won his only previous encounter with Murray back in 2011, beating the two-time Grand Slam champion in straight sets in Madrid.
"I expect a tough match," Murray said. "He's an aggressive player, he likes to try and dictate the points from the back. He's had some good results this year, won two matches here very comfortably."
Bellucci's straight-sets victories over Briton James Ward and Japanese teenager Yoshihito Nishioka to reach the last 32 stand in stark contrast to Murray's three dropped sets against Nick Kyrgios and Mannarino, but the Scot takes heart from the tests he has passed, both in this year's tournament and throughout his career.
"When you're not playing your best, you find a way to come through matches like that. Yeah, it can give you confidence. You feel a little bit like you're fortunate to still be in the event and you're a bit more maybe relaxed going into the next matches.
"But I've come through many tough matches in my career, and I think that's why when you are behind like that in the scoreline, when you've done it in the past, you have the belief that you can come through and do it again. That definitely helped me here today."