Image source, AFP

Wawrinka is looking more comfortable on court tonight than when posing with these enthusiastic fans earlier in the week.

David Law
BBC Radio 5 live sports extra commentator

"I think Stan would be in the top five if they decided to have an arm wrestling competition, rather than play tennis one week. Rafa Nadal would win it though."

A serve of 131 miles per hour, proves too hot for Federer, who can only send it into the net.

But a wild backhand from Wawrinka, after the ball zipped up off the surface, takes it to 30-30. But again his serve comes to the rescue with another one of 135mph and it is soon 3-1.

Image source, AFP

Earlier today, we asked former British number one Tim Henman a selection of questions from BBC Sport Facebook users., external Here is one of his answers.

Daz Plant: "With Liam Broady and Kyle Edmund making the finals of Challenger tournaments in the past few weeks to end the year inside the top 200, how would you rate their chances of challenging for the top 100 by the end of 2015?"

TH: "It's a very realistic goal for both of them and I think they should set their goals high. I think what Brody has done very well is compete a lot.

"I think he's played 32 or 33 tournaments this year and he's got some momentum going into next year - it's important he maintains that. Likewise, with Kyle I'd like to see him compete a lot more and if he does that and keeps improving there's no reason why he can't be top 100 by the end of next year."

Leon Smith
GB Davis Cup captain on BBC Radio 5 live sports extra

"We have a match. That's a big break for Stan. He stuck to his tactics, hitting deep heavy balls into Roger's backhand. It's the right tactic and he's got to maintain that but it's a good start from him."

Wawrinka shows his early power with a delightful backhand shot to move 30-15 in front, before then going on to have the first break point of the match.

Another blasted shot, this time a forehand, is too fierce for his opponent and Federer has his serve broken for the first time this week. He has not lost a set in his three matches at the O2 Arena this year. He has work to do to maintain that record, but what a start from Wawrinka.

We asked who you would like to see play Novak Djokovic in Sunday's final. Are there any Stan fans out there? #bbctennis

Simone Robinson: Would love a Federer vs Djokovic final as have never been to a live tennis event - first tomorrow! Just so excited!

Nuren Ahmed: Roger Federer vs Novak Djokovic is the final everybody wants to see. It will be a fitting conclusion and proper contest.

Leon Smith
GB Davis Cup captain on BBC Radio 5 live sports extra

"Stan will feel a lot better. At 15-30 it was looking a bit dodgy for him but he will feel good to get the early hold."

We said it could be good. It is already.

Wawrinka gets lucky when his shot clips the top of the net, and it is an early tester for Federer. He gallops towards the net and just gets there in time, but Wawrinka uses a deft touch to lob the ball back over his head for an exquisite winner. Wawrinka then holds when a Federer forehand is slightly wayward.

David Law
BBC Radio 5 live sports extra commentator

"Federer is seeing the ball like a football. He's got that exhibition look about him."

What a start from Federer. If he wanted to stamp his authority on the match quickly, he has done so in style with two blistering forehand shots that his opponent doesn't even have time to run for. The world number two has a routine hold to start us off.

Watch five of the best shots from Novak Djokovic's three-set victory over Kei Nishikori at the ATP World Tour Finals in London.

Djokovic, chasing a third straight season-ending title, came through 6-1 3-6 6-0 at the O2 Arena.

Russell Fuller
BBC tennis correspondent on Radio 5 live sports extra

"Federer will be delighted that Wawrinka is playing himself into a bit of form with the Davis Cup coming up but he will want to win tonight, although he won't want to damage his Swiss team-mate's confidence."

Image source, AP

Novak Djokovic saw off Japan's Kei Nishikori in three sets to reach the final of the ATP World Tour Finals.

The world number one, chasing a third straight season-ending title, came through 6-1 3-6 6-0 at the O2 Arena.

Djokovic recovered his form superbly after reacting badly when the crowd in London applauded a double fault in the second set.

So who do you want to see play Novak Djokovic in tomorrow's final and why? Can anyone stop the Serbian from winning the title for a third successive year.

Let us know on Twitter, using the hashtag #bbctennis or leave a message on the BBC Sport Facebook page., external

Piers Newbery
BBC Sport at the O2 Arena in London

"I think 6-3 6-4 - Federer." That's the verdict of Swiss journalist (and my media room neighbour) Arnaud, although he points out that there is more on the line tonight with Switzerland's Davis Cup final in France coming up next week. "We don't want Roger to win too quick and destroys Stan's confidence. The most important thing is that we beat the French."

Federer was out on court a couple of hours ago hitting with coach Stefan Edberg, a match-up that had many tennisheads here drooling at the "what if" scenario that threw up. There was a healthy smattering of Swiss fans court side already, and the O2 Arena is once again creaking at the volume of red-and-white clad fans with 'RF' and 'Stanimal' branding emblazoned across them. I reckon we might get a cow bell or two as well.

You can listen to live commentary from the O2 Arena on BBC Radio 5 Live Sports Extra. All you have to do is click on the live coverage tab at the top of this page, sit back and enjoy.

Hello, welcome back for live text commentary of the second semi-final from the ATP World Tour Finals in London. I hope you enjoyed the football and rugby, and now it's back to the tennis.

We already know world number one Novak Djokovic will be in the final, and that he will be playing a Swiss opponent in the final tomorrow. But which one?

World number two Roger Federer takes on countryman Stan Wawrinka, fourth in the rankings. We should be set for a high-quality encounter. This should be good.

Image source, AFP

Roger Federer and Stan Wawrinka have been in formidable form this year to help Switzerland reach the 2014 Davis Cup final.

Next weekend, the pair will be hoping to guide their country to the title for the first time in their history when they play France in Lille.

But that friendship will be put on hold for a couple of hours or so tonight. Team-mates become fierce rivals. Personal glory replaces national pride. Only one man can win.