US Open: Andy Murray overcomes Feliciano Lopez and the heat to reach fourth round

• Andy Murray beats Feliciano Lopez 7-6 (7/5) 7-6 (7/5) 4-6 7-6 (7/4)

For those enjoying America’s Labor Day weekend, a few hours in the sunshine may have been a pleasant way of spending the afternoon, but for the No.3 seed keen to conserve as much energy as possible, spending more time than necessary running about in the blistering heat was not a good idea. The temperature was already 90° by the time the match started and, with the humidity rising, the heat was stifling.

In such conditions, neither man was willing to risk anything. Murray may have had the better of Lopez in all their previous six meetings – indeed, he had only dropped one set to the Spaniard in seven years – but the world No.31 is no slouch.

Lopez is a rare breed, a Spaniard who likes to attack the net. That aggression gives Murray a target for passing shots but the Scot cannot afford to take his eye off Lopez for a moment. The Spaniard’s left-handed serve can be vicious and he loves to construct points with the backhand, a shot he can either caress or clobber. And all the time he is looking for the chance to come forward.

It was clear from the start that Lopez was playing well and, for almost an hour, there was not so much as a fag paper between the two men. Even when Murray found himself in a position of power with three break points – Lopez offered up a few unforced errors, closely followed by a few, choice, Spanish swearwords – he could not convert them.

Lopez grabbed them back and then went on apply a little pressure with a couple of break points of his own. That merely forced Murray to move up a gear, avert the crisis and move towards the first-set tiebreak.

Once in the shoot-out, there was only one forehand between them – Lopez missed it – but at least, after 59 minutes, Murray was a set to the good.

With his nose in front, Murray appeared to get a new lease of life. In the first set, there had been moments where he looked able to dominate but they did not last for long. As the second set began, he was on his toes and looking to punish the Spaniard.

An early break of serve put him in the driving seat but still, Murray could not put clear water between himself and his frustratingly consistent rival. A sloppy service game midway through the set put Lopez back on level terms at 3-3 and another tiebreak beckoned. And, if Murray thought that Lopez might lose heart now that he was a set behind, he was sorely mistaken. Quite the opposite, in fact.

Come the second tiebreak, Murray was on the ropes from the start. No matter, fighting his way back from 4-1 and 5-3 down, he secured a two set lead and set about Lopez again in the third. Yet again, he got the early break and, yet again, he could not hold it. He broke again for a 4-2 lead and, again, Lopez broke straight back. By this stage, they had been on court for more than two and a half hours in the blistering heat and the nerve ends were beginning to fray. When Lopez broke yet again, he leapt in the air in delight. When the Spaniard served out to take the set, Murray suddenly looked very, very tired.

But if Murray is anything, he is a fighter. He may have looked hangdog between points but, at the merest hint of an opportunity, he was ready to pounce. That moment came in the fourth set tiebreak as he ripped a backhand winner to claim a match point. At last the end was in sight and Murray was on his way to the fourth round.

Laura Robson will be hoping that, win or lose, today’s encounter with Sam Stosur is not quite so gruelling. The 18-year-old giant killer has already disposed of Kim Clijsters and Li Na on her way to the fourth round and now she is aiming to knock the defending champion off her throne. They have never played before but, with Stosur’s reputation for cracking under pressure and with Robson having absolutely nothing to lose, anything is possible.