Paul Thompson: This could be one of Leon Smith's finest hours as GB coach if this becomes a 3-2 victory. Murray continues to be inspirational...

Mike Child: If Del Potro doesn't play the last rubber, I honestly think GB can win with Dan Evans. This didn't seem possible on Friday.

Tracey Kelly: Amazing watching the support for @andy_murray!! Come on our Scottish lad.

John Inverdale
BBC commentator in Glasgow

That is how to convert a break point.

Andy Murray has the first two break points of the match at 15-40.

A baseline exchange of bluff and counter, slice and spin, ends with Guido Pella pressing to the net and slotting away the backhand volley from around shoulder height.

But the Argentine has the second break point forcibly prised from his grasp.

Murray loads up and slams a cracking cross-court winner across his chops to move a break up.

Andy Murray whips off a service hold to love.

The real intrigue though is on the sidelines.

At the game's end, Dan Evans heads off somewhere behind the scenes with Kyle Edmund staying put to support.

Leonardo Mayer is also strolling backstage. 

Are those two getting in the zone for the final singles rubber?

No sign of Juan Martin del Potro either down on the court or anywhere else.

If there are any creeping doubts in the Argentina camp as they try and close in on a first-ever Davis Cup, the visiting fans at the Emirates Arena are bluffing them off in style.

The "Oles" are ringing around as their man moves to 40-15 with canny courtcraft.

A netted backhand gives Andy Murray a sniff at 40-30, but Pella comes to the net to pat away a winning volley.

On the supporters' benches are Scottish First Minister Nicola Sturgeon and House of Commons chief bouncer John Bercow.

John Lloyd
Former GB Davis Cup captain on BBC Two

I don't think there will be that big a threat from the groundstrokes of Pella. Andy has got to be patient, play his normal game and he will be OK today.

We are lucky to have him, every match he plays is special. What Andy has done for British tennis is staggering.

Andy Murray to 40-0 in a twinkle.

Guido Pella sticks a spanner in the spokes with a well-judged lob and follow-up backhand swat.

Into an extended rally on the next point - I think we are going to see plenty of those today - which Murray nets to bring up 40-30.

Pella is sticky as pavement chewing gum, but Murray shakes him off with a rattling good ace down the middle.

John Lloyd
Former GB Davis Cup captain on BBC One

I think Andy will win but he might be out there for a long time today.

The atmosphere is absolutely simmering in the Emirates Arena.

If you could bottle it, it would certainly be on a Wada banned list.

Andy Murray to serve.

Image source, Reuters

Away from the intrigue in Glasgow, things appear more straightforward in the other semi-final in Zadar, where Croatia lead France 2-1. A victory for Marin Cilic over Richard Gasquet would take Croatia through to a home final against Argentina, or a trip to Britain. 

Jamie Baker
Former GB Davis Cup player on BBC One

Andy has been running on empty from the start. He can see light at the end of the tunnel now. If he can push one more match he can have a rest after this one.

If Andy is fit, he will not lose this match. No way.

Joe Fernandez: Loving the #DavisCup conspiracies on #bbctennis now. Sounds like DelPo off to allow a GB win! Has to be Evans post

Mr H: Would go with @Evo151216 v JMDP if Andy wins. More experience & stamina than Kyle & had a great year too.

Janet Handley: Argentina need to win just 1 don't underestimate them or the difficulty we face.

First things first though.

Andy Murray has dragged his weary bones back out onto court to face the wily Argentine Guido Pella in the opening singles rubber of the day.

They have never played each other before but, judging by his win over Edmund in the opening rubber of the tie, Pella has the canny all-court game to frustrate and infuriate.

Jamie Baker
Former GB Davis Cup player on BBC One

I would pick Dan Evans. He has been in the situation before and is the type of character he won't worry and will give the opponent a lot of problems.

He was the vocal man on the GB bench yesterday, I think he knows he has a chance of playing in the fifth rubber. He wants to be the man in the spotlight.

Image source, Getty Images

What about on the British side of that second singles rubber?

The common consensus seems to be that captain Leon Smith is leaning towards bringing in Dan Evans to face whoever Argentina put up.

It seems to make sense.

The court is not playing as fast as expected which negates Kyle Edmund's massive forehand.

Evans is in the hottest form of his career having come within one point of ending evenutal champion Stan Wawrinka's run at the US Open.

The conspiracy theorists were out in force in the Emirates Arena this morning, reading the runes from the two team's knock-ups.

Juan Martin del Potro ambled through a brief 10-minute session of lacklustre practice serves, while Leonardo Mayer went through a more thorough hit.

John Lloyd
Former GB Davis Cup captain on BBC One

It will be a staggering decision if Del Potro doesn't play. 

There are rumours Mayer will play. I find it hard to believe Del Potro won't play.

Why on earth did Del Potro play the doubles yesterday if he was not fit enough to play today?

Why would he not give himself 24 hours to recover? If it does happen, it would be the most illogical decision I have ever seen.

Image source, Rex Features

So why was Juan Martin del Potro wheeled out for a doubles match yesterday, when it is not a form of the game that he usually plays, his fitness is flaky and his presence made little difference to Argentina's underdog status in that rubber? 

"I thought that it was the best doubles team we have. We went for it to intend to close out the tie,” said coach Daniel Orsanic.

The word in the Argentine press was that perhaps Del Potro had just enough in the tank to get thorough the less taxing doubles match even if another singles match was beyond him. 

So is Del Potro a busted flush for this weekend? Doubles partner Leonardo Mayer looks the man most likely to step into the breach if Del Potro pulls out.

Image source, reuters

Juan Martin del Potro was more cryptic than the Times crossword in the press conference after his doubles defeat last night.

"I have to be smart. I want to play for more years not just one more match," he told the press when asked if he was fit and ready to play in the second singles match.

"My legs hurt, my wrist, my back, my right shoulder... but I'm still standing," he told the Argentine press.

A riddle wrapped in an enigma, delivered in two languages.

Image source, Rex Features

What will those singles rubbers be?

Well, we have the first one.

Andy Murray v Guido Pella

The second is open to a little doubt though.

At the moment it is Kyle Edmund v Juan Martin del Potro.

But that is subject to change - on both sides.