Novak Djokovic dispelled his reputation as a quitter after battling through five gruelling sets in the first round at the US Open.
World number three Djokovic looked to be heading for an early exit when he fell two sets to one and a service break behind fellow Serb Viktor Troicki but somehow summoned up the strength to fight back and win 6-3 3-6 2-6 7-5 6-3.
His incredible performance came on a day when organisors invoked the tournament's rarely used extreme weather policy and fled the stands to seek refuge in the shade from the blazing sun.
For most of his match, Djokovic was soaked in sweat and gasping for air and playing an opponent showing no signs of weariness.
It was only in the fifth set, when the sun began to set and Troicki started to wilt, that relief finally came.
"It was like, I don't know, sleeping with my girlfriend I guess kind of feeling," Djokovic told the crowd at Arthur Ashe Stadium.
Djokovic made the US Open final in 2007 then won the Australian Open the following year but has been heavily criticised for retiring from matches at each of the four grand slams, including his defence of the Australian Open.
"I've been in those situations before, played a lot of long matches in very difficult conditions, feeling very exhausted," he told a news conference. "You kind of start panicking a little bit when you don't feel great physically."