Andy Murray admits he is not "in the best shape"

What his heroics could not mask, though, was how far away from top shape Murray was. He looked heavy-legged throughout, was puffing hard from the first few games and was pushed well behind the baseline by 23-year-old Griekspoor, who has never played a grand slam match.

Murray had looked unexpectedly close to peak form and fitness in his remarkable title victory in Antwerp a month ago but admitted that he had put on a few pounds in the weeks since as the arrival of his son Teddy took his focus away from the court.

"I told you guys I wasn't feeling in the best shape coming in, and it showed a little bit in the match," said Murray.

"The weight and things like that, that's my fault. I've never had that in my career before. Something as you get older you need to keep a closer eye on. I won't put myself in that position again.

"If you're weighing four or five kilos more than you're used to, that is probably going to affect how you feel moving around the court and stuff. So I need to do better with that."

Murray looked exhausted at the end, while he also appeared to be struggling with a cold, so there is every chance he will sit out Britain's clash against Kazakhstan on Thursday, with Kyle Edmund waiting in the wings.

Murray said: "It's not if I want to have a rest, it's what is the best thing for the team. I could say, 'Yeah, I want to play tomorrow's match' right now, and I have no idea of how I'm going to feel in the morning, which would be stupid."

Murray's preparations were not helped by the Netherlands springing a surprise by selecting Griekspoor instead of Botic Van De Zandschulp, who played against Kazakhstan on Tuesday.

Murray denied the British team had taken this match lightly but conceded the result could easily have gone the other way.

Speaking on court, he said: "He played brilliant. I was lucky at the end of the match. He deserved to win."

Murray certainly did not lack support, with Union Flags aplenty as a sizeable contingent of British fans made the third arena at the Caja Magica look the fullest it has so far this week.

It had the feel of a Davis Cup tie but British confidence turned to something a lot more edgy as it quickly became clear Murray was a long way from his best and Griekspoor offered significantly more than his ranking suggested.

Murray, though, drew on his back catalogue of memorable comebacks to somehow find a way across the line.

He said: "I was obviously in difficult positions, like 5-4 in the third, 15-30, and was down in the tie-break, so it's getting pretty close there.

"But I've found a way to win matches many times in my career when I've not been playing well. You can draw on that a little bit. I came up with some really good defensive shots at the end of the tie-break.

"It is about finding a way to win, and I did that today. And I'm proud of myself because it would have been easy to have lost that."

Murray's victory became even more important when Dan Evans was beaten 3-6 7-6 (5) 6-4 by Robin Haase to send the tie to a deciding doubles rubber.

Evans looked to be cruising at a set and a break up and served for victory at 5-4 in the second set but Haase, who is ranked a lowly 163 but has been as high as 33, broke back and won the decider.