Defending champion Andy Murray withstood some heavy hitting from Argentina's Leonardo Mayer to reach the third round of the US Open in four sets.
Murray, seeded third, dropped his first set of the tournament as he came through 7-5 6-1 3-6 6-1 in two hours and 41 minutes.
He will face Germany's Florian Mayer, the world number 47, in the last 32 on Sunday.
"I didn't feel like I served as well today as I did in the first match (against Michael Llodra) - different court, different conditions during the day," he said.
"I finished the match well today. I played well when I needed to - that's a good sign.
"I want to keep improving as the tournament goes on. You don't want to play your best right at the beginning, so I hope I can get better."
British number one Murray, 26, has had some tough matches on Louis Armstrong Stadium in the past and was tested once again on a sweltering day in New York.
The allure of the reigning and champion was plain to see as a huge queue formed outside the second show court at Flushing Meadows.
Those who made it inside might have been forgiven for thinking a shock was on the cards as Murray laboured in the early stages, and then dropped the third set to a free-hitting Mayer.
The world number 81 started confidently, earning two break points in the opening game as he dictated with his forehand, but could not grab the break he was pushing for, and eventually his level dropped.
Four errors in a row - three of them forehands - handed Murray the first break at 6-5 and the Scot served out the set with little fuss.
Murray dropped just one game on his way to taking the second in 35 minutes, but his first-serve percentage was still hovering around the 45% mark and it allowed Mayer a way back into the match in the third set.
The Argentine thumped one of those massive forehands to break and moved out to a 3-0 lead that he would not relinquish, coming up with another forehand and an ace to keep Murray at bay in the seventh game.
With the temperature cooling as the sun dipped behind the stand, Murray knew he was in a battle and fired himself up at the start of the fourth set, repeatedly telling himself to "Come on!" and berating the umpire for failing to overrule a call.
It was now a pulsating contest as Murray strained to regain control and Mayer hit back with some huge hitting, but the world number three finally got his way in game four.
Murray played a brilliant opening point of trademark scrambling behind the baseline and went on to break to love for a 3-1 lead, repeating the feat two games later and firing a magnificent cross-court forehand winner of his own while closing out the match.
"It's a court I haven't played my best tennis on, that's for sure," Murray said.
"[But] I'm happy to play on any court. It doesn't really make a huge, huge difference. We got a great crowd out there; it was a really good atmosphere from pretty much the first point through to the last.
"Whether or not I've played well on that court, it's always a really good atmosphere. It's normally packed and it was the same again today."