Roger Federer faces fellow-Swiss Stanislas Wawrinka in the second semi-final on day seven at the ATP World Tour Finals at the O2 Arena in London.
Where to Watch
Roger Federer v Stanislas Wawrinka is live on Sky Sports HD3 and BBC Radio Five Live Sports Extra from 2pm.
Just six days prior to the start of one of the biggest weeks in Switzerland's tennis history, its two main protagonists Federer and Wawrinka go head-to-head in London.
Teammates against France in the Davis Cup final next week, for now the duo are rivals bidding for a place in the ATP World Tour Finals after a comfortable route to the last four.
Federer overwhelmed Milos Raonic, Kei Nishikori and Andy Murray to qualify top of Group B while Wawrinka recaptured his very best in beating Tomas Berdych before easing past Marin Cilic on the final day of qualifying.
The 17-time grand slam champion holds the overwhelming advantage of the head-to-head record, having won 14 of their 16 matches, including the last in London in the Wimbledon quarter-final.
Wawrinka has never beaten Federer on any surface other than clay and despite having a grand slam to his name in 2014 in the form of the Australian Open, he is the huge underdog in the second semi-final of the penultimate day of competition.
What they said:
Roger Federer: "It's an extra match for Stan, in particular. It's an opportunity for both of us to play a quality match ahead of Davis Cup. But honestly Davis Cup is so far away in my mind right now. We care about playing very well here. I'm very happy I'm getting to play an extra match because I want to arrive in France with a lot of matches in my legs. I wouldn't want it any other way. I'm happy that Stan has also picked up his level."
Stanislas Wawrinka: "It's going to be a tough match for me, for sure. But I will have to play my best game if I have a chance to beat him. I know I can do it. I know it's going to be very difficult. I have seen him play the first three match. It's always the same. Indoor, if you don't stay with him at the beginning, then it start to be really tough."
Betting odds (source: William Hill):
Roger Federer 1/6 v Stanislas Wawrinka 7/2
Head-to-head record: Federer 14-2 Wawrinka. Last match Wimbledon (Hard) Federer bt Wawrinka 7-6(5) 6-4 6-4.
Previous meetings at the ATP World Tour Finals: N/A