ANDY Murray was beaten but unbowed last night after losing his first-ever Davis Cup singles rubber on home soil over five hours to Juan Martin del Potro. The 29-year-old World No 2 said he was "proud" of the performance he put up during his 4-6, 7-5, 7-6 (5), 3-6, 4-6 defeat by the resurgent Argentine - and hadn't considered withdrawing from the tie to join the mourners at his paternal grandfather Gordon's funeral in Kilsyth yesterday.

At five hours seven minutes, the re-run of the recent Olympic final between the two players was the longest match of both men's careers to date. Coupled with Guido Pella's 6-7 (5), 6-4, 6-3, 6-2 victory against Kyle Edmund, it left Great Britain trailing Argentina 2-0 after the opening day's singles as they endeavour to retain the title which they claimed for the first time in 79 years in Ghent in November. It is their first such deficit since a remarkable recovery in a World Group play-off against Russia in Coventy in April 2013 but they didn't have a player of the calibre of Del Potro in their ranks.

Typically Murray refused to use his exertions of the summer or the strain of his recent family bereavement as excuses for his defeat, but said he would decide this morning whether he will partner his brother Jamie in today's doubles rubber against Federico Delbonis and Leonardo Mayer. While no-one in the Great Britain camp was admitting defeat, Argentina now have the luxury of keeping Del Potro fresh for the return singles, against either Edmund or Dan Evans. It may only have been a precaution, but Evans was hitting on the Emirates Arena court last night.

"It has been hard," Andy admitted, about the strain of missing his grandfather's funeral. "But I always planned on playing. I did great today - I’m very proud of how I played. I thought I did fantastic. I fought for every point, tried as best as I could. That’s all you can do.

"I’ve never played a match that long, so we’ll have to see how I am when I wake up," he added. "I will probably make a decision then. But I’ve never played a match that long. I’ve played matches close to that length but none after an extremely long stretch of playing. So I don’t know how I’ll feel when I wake up.

"Doubles is always a tough match. And if I recover okay, I’ll be the favourite to win the match on the Sunday. There’s no reason why Kyle or Dan couldn’t push Juan hard. But we’ll have to wait and see how the weekend plays out."

While Smith said it was one of his most disappointing days as captain, he was insistent his team wouldn't give up the fight. He too was unsure whether both Murray brothers would be sighted on doubles duty today. "We've had a lot of good days but especially where we are in the World Group, playing against great teams, you are going to get days like that," said Smith. "Both guys have fought as hard as they can, given as good as they get and that is all you can ask. We are still in it, we have to keep fighting. We are very proud as a team what we have achieved so far so all you can ask is that we go out and fight."

The World No 2 said he felt the quality of yesterday's match had been even greater than the Olympics final, and praised the behaviour of partisan crowd save for a small group of Argentinian fans whom he rebuked for making noise while he prepared to serve.

"It’s very fine margins," said Murray. "That happens in tennis, in sport sometimes. It could have gone either way. He just played a little bit better in the fifth set.

"The Olympics match was extremely close as well," the Scot added. "Maybe the quality of this match was a little bit better. It didn’t feel like there were loads of unforced errors or mistakes in important moments. It was good tennis that was winning the match I think.

"All I was saying, in between serves, was keep the noise down. That was it. There was no need to be making noise between first and second serves."

Del Potro said the victory was a special moment. “I'm so tired," admitted Del Potro. "I’ve got cramps everywhere. It was the longest match of my career and I won it against Andy playing here, so it’s very special for me. It could be revenge [for Rio] but in that match I was exhausted right before the final and now I felt I could fight for the five hours and five sets. I think we made a good choice with the captain to play Andy on the first day.”

The other Davis Cup semi-final, between Croatia and France, in Zadar, is locked at one rubber apiece after the first day.