Great Britain must win both singles matches against Argentina on Sunday to extend their reign as Davis Cup holders and reach a second final in 12 months.
Andy and Jamie Murray won Saturday’s doubles contest, but Argentina lead 2-1 going into the last day of the best-of-five tie in Glasgow.
Andy Murray is scheduled to face Guido Pella at 13:00 BST, followed by Kyle Edmund against Juan Martin del Potro.
However, team captains can change their nominations up to an hour before play.
GB skipper Leon Smith could choose to bring Dan Evans in for Edmund, should Murray beat Pella and force a decisive fifth match.
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And there is a question mark over the involvement of Del Potro, who was a surprise inclusion in the doubles after his gruelling five-hour match with Andy Murray on Friday.
Del Potro hinted after the doubles that he might not play on Sunday, should a fifth and final rubber be required.
“I have to be smart,” said Del Potro. “I want to play for more years not just one more match.”
Jaded Murray to give ‘best effort’
Andy Murray is clearly fatigued after a gruelling summer but hopes he has enough energy left to produce a win to keep GB’s hopes alive.
The 29-year-old Scot said: “Whether I win or not, I don’t know, but I can definitely guarantee I’ll give my best effort and hopefully I can.
“I’ll be tired and I have to accept that and deal with it and try to play the match on my terms if possible.”
Speaking about the doubles success, he added: “I didn’t know how I was going to feel when I woke up.
“I saw my physio this morning and he checked some of the things he checks if I’m not feeling great or if I’m tired, and he said I was looking decent.
“It was tough, obviously. In doubles there’s not as much running but you need to be very sharp.”
Russell Fuller, BBC tennis correspondent:
“Juan Martin del Potro’s appearance on the doubles court was a huge surprise, given Argentina’s position in the tie, and it may turn out to be his last match of the week.
“Both del Potro and Andy Murray have now spent eight hours and two minutes on court in Glasgow, and although mind games are often an important ingredient, Del Potro has hinted quite strongly he may not play on Sunday should a fifth and final rubber be required.
“The travelling Argentine media are inclined to take his words at face value – and suspect he won’t play.
“Dan Evans is likely to play in any fifth match for GB – but that will only be necessary if an equally exhausted Murray can first beat Guido Pella, who will be feeling a lot, lot fresher.”
Article source: http://www.bbc.co.uk/sport/tennis/37398571