In what was only his ninth match since returning from hip surgery, Murray went toe-to-toe with the 31st seed in blisteringly hot conditions during the second round in New York, before succumbing 7-5 2-6 6-4 6-4.

There were signs of the old Murray in some of the defensive lobs he hoisted, the backhands he drilled into the corners and, in particular, the fire he showed in a fourth set he almost turned around.

But there was also the now-familiar limp, too many double faults and an understandable lack of match tightness that meant it was Verdasco who came out on top for just the second time in their 15 meetings.

Andy Murray leaves the court following defeat to Fernando Verdasco. Picture: Getty

Murray knows it is still very early in his comeback and playing two tough best-of-five-set matches will stand him in good stead, but these are baby steps and his ranking remains outside 300.

The 31-year-old remains optimistic he can get back to his best and arrive at grand slams with ambitions to win titles again, rather than simply a match or two, but he knows there are no guarantees.

He said: “There’s for sure doubts because you just don’t know. When I got the injury, I was ranked number one in the world. Twelve months later, things completely changed.

“You just don’t know exactly what’s round the corner. If things keep going smoothly, physically I continue to improve, I believe that I will get back to competing for the biggest competitions because there’s no reason why I couldn’t.

“But when you continue to build up and start playing more tournaments, you don’t know how you’re going to respond.

“Because of the path that I’ve been on the last year with the many, many ups and downs, trying to come back, it not quite working, then ending up having the surgery and stuff, I think it’s completely normal to have those doubts.”

Murray’s verdict on his performance against Verdasco was mixed, with the Scot’s major regret that he did not win the first set having recovered from a break down to lead 4-2 and then held a set point at 4-5, which his opponent saved with an ace.

Murray responded well in the second set but lost energy at the start of the third, with his revival coming too late to save it.

The pair headed into the locker room for a 10-minute heat-relief break, and Murray returned to the court fuming after believing he saw Verdasco talking to his coach in violation of the hastily-implemented rule, an accusation the Spaniard flatly denied.

Murray made it clear just what he thought of Verdasco’s protestations in an Instagram post, saying: “I’m off to get a health check as apparently I’ve started imagining things,” followed by the hashtag “liarliarpantsonfire”.

Whatever the truth, Murray rarely plays better than when feeling aggrieved and he found another level early in the fourth set, but Verdasco weathered the storm and then claimed the crucial break when his opponent played a poor seventh game.

Murray almost recovered the damage, forcing five break points on the Verdasco serve and saving two match points, one with a searing backhand, but it was not quite enough.

“I think some of the tennis I played today was some of the best I’ve played since I had the surgery,” said Murray. “But there were also periods in the match, especially in the first set, where I really didn’t play particularly well.

“I hit a lot of mistakes when I was up in that set. I feel like I should have won the first set and didn’t.

“Then at the end when my back was against the wall, I came up with some good tennis to make it close and interesting and almost got myself back into it.

“There were too many ups and downs for my liking.”

Andy Murray out of US Open after four-set defeat to Fernando Verdasco