Andy Murray was relieved to make it through to the quarter-finals of the US Open in tricky conditions at Flushing Meadows.
It was not a totally convincing performance from the defending champion against Denis Istomin but he did what he had to do to come through 6-7 (5/7) 6-1 6-4 6-4.
Murray has become a master at negotiating such hurdles at grand slams but he will need to play a lot better if he is to get past old rival Stanislas Wawrinka in the last eight.
The Scot played his previous match against Florian Mayer in stifling heat and humidity but it was cool and windy on Arthur Ashe for his night-time clash with Uzbek Istomin.
The first set was cagey from both players but it was Istomin who clinched it by winning the final four points of the tie-break.
Murray responded well, as he invariably does in such situations, but he never looked comfortable and celebrated in a manner that indicated how much of a struggle it had been.
The Scot denied he was troubled by his long-term back problem, saying: “I’m just a bit stiff today. It was extremely cold on the court, very windy.
“Often when you heat up and then sometimes in between sets or if you have quite a long break, with the wind, you cool down pretty quickly.
“It was very, very different conditions to the last few days where it’s been very humid and you have been sweating a lot.
“I wanted to just try and get through the match.
“With the way he plays, he hits the ball pretty big and flat on both sides, his strokes are pretty low and hard at times to control. He made it very difficult for me.
“With the way the third set ended up going, I was just very happy to get it done, because he had chances at the end of the third set to go ahead.”
Wawrinka, who is having a great season and knocked out fifth seed Tomas Berdych, was the last man to inflict an early grand slam defeat on Murray when he beat him in the third round in New York in 2010.
Since then Murray has reached at least the quarter-finals at his last 11 slam tournaments he missed the French Open this year through injury.