John McEnroe
Three-time Wimbledon singles champion on BBC TV

Wawrinka is like a cat with nine lives. Murray is more consistent at the higher level, he will be ready, is more confident and will swing hard but I wouldn't put it past Stan the Man to step up.

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Jamie Murray on BBC Two talking about his brother's chances against Wawrinka: "Andy needs to dictate the points against Wawrinka. The court is fast so it's not as easy to defend but Andy is a bit of a man on a mission. He hasn't played his best tennis so far so he'll have to step it up."  

Image source, Reuters

Jamie Murray, speaking to BBC Two: "It's very exciting. It's a strange way to do it in the end but we've had a great year and won some big tournaments."

Image source, Reuters

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Up tempo 'tennis house' is the music of choice as the players walk on to the dark-ish blue court.

Wawrinka looks relaxed. Murray looks confident.

The Swiss world number three wins the toss and chooses to serve first.

Former British number one Tim Henman on BBC Two: "If Murray doesn't come out and play a solid match then it could be very hard for him."

Former British number one Andrew Castle on BBC Two: "With Wawrinka, when he's flowing, his highs are very, very high. When he plays world numbers one in Grand Slam finals he beats them. He's playing Murray with a chance to break his heart."

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Image source, EPA

Staying with the Murrays, what a 'Merry Murray Christmas™' it promises to be after Andy's brother Jamie and Bruno Soares sealed the men's doubles world number one spot after Nicolas Mahut and Pierre-Hugues Herbert lost their ATP Finals doubles match to Henri Kontinen and John Peers.

Who carves the turkey?

So that was a marathon explanation, which follows two days after Murray's marathon match against Japan's Kei Nishikori.

That was a tournament-record three hours and 20 minutes.

Here's what the Scot with super stamina said afterwards: "I'm just getting up each day and trying to give the best of what I have on that day.

"I'll just try to use a good rest day to recover. Hopefully I won't be too stiff and sore come Friday, but it's not ideal to play matches of that length at this stage of the season."

Image source, Rex Features

... as possible.

Hello again. It's the final day of round-robin matches at the ATP Finals. 

First up is current world number one Andy Murray v Swiss US Open champ Stan Wawrinka - you can watch that match here and on BBC Two.

There are two semi-final places up for grabs from the John McEnroe Group - Novak Djokovic and Milos Raonic are already through.

So courtesy of BBC Sport's Piers Newbery, here is what needs to happen.

Murray needs to qualify for the last four to maintain his hopes of ending 2016 as the world number one, ahead of Novak Djokovic.

The only way Murray can be eliminated after winning his opening two matches is with a straight-set defeat by Wawrinka, followed by a Kei Nishikori win over Marin Cilic (20:00 GMT).

To win the group and avoid playing Djokovic in the semi-finals, Murray must either win, or lose in three sets and hope Nishikori beats Cilic in three sets.

Happy? Confused?

Just stay with us, it'll all become clearer during the match.