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Andy Murray battled his way past Denis Istomin and into the quarter-finals of the US Open.
It was not a totally convincing performance from the defending champion, who again made a slow start, 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 26-year-old said: ``It was definitely tough. It's pretty breezy out there. Both of us were struggling with our timing early on. I thought we played some entertaining points.
``I started trying to dictate the points a bit more, used my forehand a bit more. I had a few chances to win the first set so it was just minor adjustments.''
Wawrinka 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.
Murray said: ``It'll be a very tough match. He's played great tennis the whole year. He's a very talented player. We played once before on this court (in 2008) when we were much younger but a lot has changed since then.''
Murray had struggled with his breathing in extreme humidity during his third-round win over Florian Mayer, but the cool and breezy conditions that greeted him as he strode onto Arthur Ashe could not have been more different.
They presented their own challenges, and the opening exchanges were cagey as both men tried to find their rhythm, Murray serving two double faults in his first game.
World number 65 Istomin is unique among top-level men in being coached solely by his mother Klaudiya, and he is a talented shot-maker who has given a lot of the leading players some trouble.
The pair had met once before, in Brisbane earlier this year, with Murray winning in two close sets.
The Scot made another unconvincing start and a poor game helped Istomin make the first move of the match with a break for 5-3.
It was not a high-quality encounter, and the Uzbek promptly handed the break back with an iffy game of his own, finishing with a double fault.
Istomin then played to the crowd with an ill-advised attempt at a shot through the legs when well placed to hit a winner.
It was that sort of match.
The tie-break was equally tight and, after Murray had edged ahead 5-3, Istomin played the point of the match before a double fault from the Scot levelled matters again.
Murray then netted a forehand to give Istomin a serve to clinch it, which he did when his opponent drilled a backhand wide.
It was the second set Murray had dropped during the tournament after losing the third against Leonardo Mayer in the second round.
He made a much better start to the second, a fizzing forehand helped him break in the second game.
Murray was using the drop shot a lot, mostly to good effect, but Istomin got his own back with a precision effort to save the second of three break points at 1-4.
But a fourth arrived and this time Murray took it with a return that Istomin could only scramble wide.
The third seed was much more in control now, but Istomin had the satisfaction of winning a point with a between-the-legs shot before Murray took the set.
The third set was a mixture of the very good and the sloppy from Murray, who broke for 2-1 only to give his advantage away three games later.
His forehand was beginning to really fire, though, and he finally converted a fourth chance to break in the seventh game.
There had not been too much to bring the crowd to their feet but the first point of the next game certainly did as Murray used all his legendary defensive powers before hooking a passing shot past the helpless Istomin.
This time he did not falter, securing the set with an unreturnable serve.
Murray seemed well on his way to a quarter-final meeting with Wawrinka, who knocked out fifth seed Tomas Berdych, but he could not put Istomin away.
In the end it was a huge stroke of luck that helped him clinch the crucial break of serve in the ninth game. Murray had seen one break point come and go when he framed a forehand high into the night sky.
Amazingly it dropped in and the third seed capitalised before serving out the victory in three hours and seven minutes.