Murray's in contention again in Wawrinka's service game at 30-30, but his backhand return is poor and finds the net.

But the world number one's next return from out wide lands right on the line which cramped up the Swiss. Deuce.

Chance! Murray has the first break point of the match after a Wawrinka error.

The Scot takes it by coming into the net and forcing another error from the Swiss. It was coming to be fair.

Wawrinka needs to break back - sharpish.

Andrew Castle
BBC Sport tennis commentator

Murray is changing the pace every now and again during the rally, taking the pace off the ball so Wawrinka doesn't have as much power to play with.

Andrew Castle
BBC Sport tennis commentator

We're seeing an amazing passage of play from Stan Wawrinka.

Rally o'clock - the longest rally of the match (about a million strokes, I think) ends with a Wawrinka unforced error on his backhand.

Stan bites back with a forehand laden with heavy topspin, before Murray makes it 40-30 by killing Wawrinka's passing shot at the net.

Another error by the Swiss from the back of the court sees the Scot seal his third service game. This is tight.

Image source, Reuters

Andrew Castle
BBC Sport tennis commentator

Stan's Mum and Dad are here today - that might explain why he's seemingly so eager to impress.

Piers Newbery
BBC Sport in London

Roger Federer might be absent this year but it looks like his Swiss fan club have still made their annual trip to London - we've heard "Allez Stan!" as much as "Come on Andy!" in the opening stages. During the Federer glory years we sometimes even heard cow bells, although you might struggle to get them through security now. Every cloud...

Actor Kevin Spacey is in the crowd to watch the match - all the usual suspects have turned up this week.

Wawrinka yet again has a 40-0 lead but then loses concentration - he's 40-30 after a poor volley at the net.

But the world number three makes no mistake with the next point - another ace from the Swiss.

Patrick Brennan: If everyone plays to their current max, Djokovic wins. No-one else more stubborn than him. Until his injuries, it was Nadal.

Ally Siu: Andy Vs Stan is definitely being prioritised over work right now!

Andrew Castle
BBC Sport tennis commentator

You can see the signs of wear and tear on Andy Murray as he holds his shoulder. It was a really physical game against Kei Nishikori the other day, they both did a lot of running.

The O2 is lit up like it's about to host an N'Sync concert - but no it's...er...it's...er..well.. it's not. I couldn't think of an N'Sync-tennis related pun. I've been told N'Sync aren't around anymore either.

Murray has started as well if not the better than his opponent. He's mixing up his groundstrokes and it's hard to predict whether he's going to come in or stay back.

He wins the service game by changing his forehand return to a more looping one which baffles Wawrinka at the other end.

Image source, Reuters

Wawrinka is a machine at the mo - he must have had three wheat blocks for his brekkie this morning. He races into a 40-0 lead.

But what's this? Murray starts to read his opponent's serves when all looked lost. A return is met with a wayward throw of the racquet from Wawrinka - it's suddenly deuce.

After a mini-game at deuce, Wawrinka wraps his second service game with an ace. That was perhaps a wee bit more tough than the Swiss would have liked.

Andrew Castle
BBC Sport tennis commentator

I don't know if this will last the whole match or not, but when Wawrinka comes to play like this there's nobody who can live with him really.

Tim Henman
Former British number one on BBC Two

It's a hypothetical argument... but if every player on the Tour plays to their absolute best - who wins?

Interesting question posed by Tim. Perfect fodder for a Friday afternoon debate in the live text...

Tim Henman
Former British number one on BBC Two

This is a fearsome start from Wawrinka. In Murray's previous two matches, I didn't feel like his timing was quite right and Wawrinka can take advantage of that today.

What a fierce return by Wawrinka - he hits a forehand dead to put himself 30-15 ahead of Murray's serve.

The Scot bites back with a forehand wide of Wawrinka's reach before a heavy serve is misread by Stan.

From power to subtlety as Murray wins the game with a delicate dropshot.

We're all square.

Neil Foot: Why would Murray want to avoid Djokovic in the semi-final? Right now he has the beating of him and would guarantee #1 if he did.

A great start by Stan - two winners in the first two points. He already looks 100% better than he did in his opening match against Kei Nishikori. He couldn't be much worse to be honest,

The Swiss world number three follows it up with a swipe of a backhand and forehand to win his service game to love.

Murray WILL have to be at his best by the looks of it.

Image source, Reuters

Tim Henman
Former British number one on BBC Two

Andy has to make sure he's focused on this match. If he's a little bit distracted like he was against Kei Nishikori two days ago then this could be difficult. They are both capable of beating each other - the start is important