New York: Andy Murray battled back from two sets down to beat France`s Adrian Mannarino at the US Open before calling for new rules to cut the number of retirements, which have hit record levels.
Third seed and 2012 champion Murray triumphed 5-7, 4-6, 6-1, 6-3, 6-1 after his world number 35 opponent had threatened to condemn him to his earliest loss in New York since his debut in 2005.
But left-hander Mannarino wilted in the 30-degree heat and humidity in Arthur Ashe Stadium as Murray`s better physical condition proved crucial.
Murray goes on to face Brazilian 30th seed Thomaz Bellucci for a place in the last 16.
With heat and injury-forced retirements now at a record 12 in the men`s event -- including 10 in the first round -- Murray called for a heat rule, similar to the women`s tour, to be introduced for the men.
"When it`s extremely hot and humid, it helps to have that break," said Murray of the 10-minute rest that women players take between the second and third sets when the temperature goes above 30.1 degrees.
"I don`t know exactly what it`s for. But I guess you get the chance to sort of go off and change, get under a cold shower if you want to."
Murray also suggested new measures to prevent injured players turning up at events but going through the motions on court before stopping in a brazen ploy to claim the prize money.
The British star believes that "Lucky Losers" from qualifying should be given the opportunity to play in the main draw instead.
"If someone`s injured before they go out there, they`re just going to play five games or a few games just to get the first-round cheque, then that`s really bad for anyone that`s paid to come and watch," he said.
"So the best thing to do, if you`ve worked the whole year to get into these events and earned the right to play, if you show up here and withdraw, give the lucky loser a chance.
"But the player that pulls out takes the first-round prize money. If I was the lucky loser, I`d be delighted to have the chance to play for the second-round prize money.
"I think the player that`s earned the right to be there in the first place, you give them the first-round prize money and you avoid people walking on the court for a few games. It`s a waste of time for everyone."
Murray, who has been suffering from a cold in common with many players at the tournament, admitted the conditions had been tough on Thursday as he pulled off his eighth career comeback from two sets down.
"I`m proud of the way I fought. It was not an easy match to come through at all. He was making it extremely difficult for me, as well," said Murray.
"I was very happy with the way I fought through that, you know, finished the match stronger than him."
Murray, who had needed four sets to beat Nick Kyrgios in the opening round, fired 21 aces -- the last of which was on match point -- while Mannarino was undone by 61 unforced errors.
It was a familiar tale of woe for the 27-year-old Frenchman, who also had a two sets to love lead over Feliciano Lopez at the Australian Open in January before retiring with heat exhaustion in the fourth set.
"In a Grand Slam match, against these kinds of a players, it is never finished, even with a two sets to zero lead," said Mannarino.
"It was there that you could see the difference between us."