It would be wrong to say that his third round opponent, Feliciano Lopez, was unfancied going into this match – Andy's mother Judy had previously taken a shine to him through the medium of Twitter – but the 30-year-old from Toledo had taken a solitary set against the Scot in their six previous meetings, and few outside his camp expected him to reverse that trend yesterday.
But amid searing temperatures of around 100 degrees fahrenheit out on the Louis Armstrong court, this match turned into the tennis equivalent of the duel in the sun, the world No 31 forcing his counterpart to work up a serious sweat en route to his 7-6 (5), 7-6 (5), 4-6, 7-6 (4) victory in a clash that lasted three hours and 53 minutes.
The triumphant world no 3 said afterwards: "It could have gone either way. Physically I would like to be in better form but these matches help with that. Normally after Wimbledon I have three weeks in Miami to get used to these conditions. This year I didn't have that because of the Olympics. It is a nice problem to have, though."
This was the second successive year these two had met at this stage, Murray permitting the Spaniard just seven games in a night match 12 months previously. That encounter saw the Scot take the first 14 points without reply and it seemed like we were in for more of the same when the Olympic Champion sent down two imperious aces to win the opening service game to love.
The Real Madrid fan – watched by former Barcelona boss Pep Guardiola – has an atypical game for a Spaniard, with a booming serve and a habit of making regular journeys to the net. We suspected we might have a match on our hands when he immediately answered the Scot with a service game of his own to love.
Break points came, and went, soon enough, though. In the very next Murray service game, the Scot had three to save, escaping on one occasion with a forehand which was shown by Hawk-Eye to have landed clean on the line.
The match would be won by whoever could dictate terms at the net and when Murray began coaxing his opponent in then eliminating him with either a devilish lob or a precise passing shot you sensed he was starting to settle.
The pressure on the Spaniard's serve reached a crescendo in a taut 10th game in which the Scot was unable to convert three set points, the 25-year-old from Dunblane taking his turn to be only a matter of millimetres away from the breakthrough.
Soon it was the Spaniard's chance to grasp the impetus, a glimpse of the new placid Murray coming as he exchanged a joke with a ball boy before sending down another booming ace as he saved another two break points.
We arrived at tie break No 1,with Murray keeping his points as short as possible. He rattled off two aces and a couple of service winners, one on second serve - only for the Spaniard to stay alive by virtue of a net cord and at least one shot which struck the frame of his racquet. The resistance proved futile when the Spaniard could only net on Murray's fourth set point.
The Scot was on the surge now, breaking the Lopez serve early in the second set to leave Lopez muttering profanities at himself.
But for once, the 30-year-old found some answers. He conjured a service break for 3-3, working himself into a righteous fury when venting at an umpire who said he had taken too long to challenge a line call.
Before long we were back in breaker mode, and the Scot was seriously up against it. He was both 4-1 and 5-3 down, but set point arrived when he correctly challenged a Lopez return which flew into the tramlines. His lead was doubled with a ball which found the frame of the Lopez racquet and flew into the crowd.
Amazingly, we were just getting started. Twice the Scot was a break to the good in the third, only to surrender the advantage, and soon it was Murray who was in meltdown and the Spaniard who was skipping back to his seat and punching the sky like his friend Rafael Nadal, en route to clinching the set.
It was remarkable to see, not least because Lopez had been on court for hours against his countryman Pablo Andujar in the last round. Everything was a struggle in the fourth set as the heat took its toll on both men's legs.
This was mano a mano, both men having multiple break point chances but being unable to capitalise as we progressed into the third breaker of the day. The day was done when a terrific passing shot set up match point and Lopez could only net.
Ultimately, this was the Scot's 250th hard court victory, and his 10th win in a row against left-handed opposition. The weather had been more Spanish than Scottish, the opposition his mother's idea of hot stuff. But Murray had proved once again that he can withstand the heat.
There was further good news, albeit slightly less dramatic, for Scottish tennis yesterday when
Colin Fleming and Ross Hutchins moved into the third round of the men's doubles with a 7-5, 6-3 win against Brian Baker and Rajeev Ram.
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