It'll be the 26th time these two great rivals engage in battle when Roger Feder and Rafael Nadal meet at the O2 Arena, London, in their second group B round-robin match at the ATP World Tour Finals.
It will also be the first time they're meeting since the French Open final, earlier this year, where Nadal managed a 7-5 7-6 (3) 5-7 6-1 win over his Swiss rival. Nadal won his 10th Grand Slam on the occasion and against an apt opponent.
However, a year ago, in the final of the World Tour Finals 2010, Federer defeated Nadal to take the championship and considering the form he is in going to the match, it'll take some doing to stop the 16-time Grand Slam winner.
Interestingly, in their three previous indoor meeting, all of which came in the season-ending Tour Finals, Federer prevailed although Nadal leads the head-to-head 17-8.
It makes for an interesting viewing, even though it won't have any direct influence on the destination of the title.