Last year's World Tour Finals saw Federer display some of the best tennis of the year, as he won his fifth title, only losing one set on the way. This year, the Swiss Maestro is qualified for the 10th year in a row, and will seek to avenge his worst season since 2002, while becoming the first man to win six trophies at the season final.
Rafael Nadal will seek to win his first and solve the Novak Djokovic riddle, while Djokovic will try to finish his record-breaking season on a high. Andy Murray is the fourth player, who's already qualified, and given his recent form, he's in the mix for winning the biggest trophy of his career.
But who will join and challenge the big four in London?
40 days are left before the World Tour Finals begin. That leaves the players with about a month to gather points and qualify. So where can they do that, and who stands the best chances?
There are two Masters remaining, one in Shanghai this week and one in Paris next month. Additionally there are two ATP 500 tournaments in Valencia and Basel coming up and a number of ATP 250 tournaments.
As already mentioned, the big four are the only ones who are qualified as of now. The ATP race looks like this.
It will be clear that David Ferrer at 3700 points this year, leading Tomas Berdych (2865), Mardy Fish (2850) and Jo Wilfried Tsonga (2780), is as good as home safe.
But Berdych, Fish and Tsonga are also very well positioned to remain in the top eight and qualify for London as they have made quite a 500-700 points gap between them and the next group of players.
While not a foregone conclusion yet, it would take some great play from the players ranked outside the current top eight to upend them for the spot, not least given the fact that Tsonga, Berdych and Fish are all looking great.
Moreover, while Berdych, Fish and Tsonga are all playing in Shanghai, some of their closest competitors are not there. Robin Söderling is still dealing with his mono, Del Potro is not present, and neither are Gael Monfils or Richard Gasquet.
Nicolas Almagro is best positioned at 2280 points, 500 behind Tsonga, but the Spaniard is no king on the hard courts, and has at best shown mediocre results as of late. However, he's handed a favourable draw in Shanghai, and could make the quarters.
The next four players are a further 200 to 250 points back (and 700-750 points behind Tsonga) and it is here we shall find the most likely challengers to a spot at the WTF. Two of them are Delpo and Söderling, neither of whom is playing. The other two are Gilles Simon and Janko Tipsarevic.
Given Almagro's recent form and his less than stellar hard court credentials, Gilles Simon and Janko Tipsarevic are probably the only two outside the current top eight with a realistic chance of securing themselves a spot at the WTF.
They've both shown great form of late, but will have to pull out something big in the coming month to pass Berdych, Tsonga or Fish.
Can Simon or Tipsarevic do it? Unlikely, but they have a shot. Can someone else do it? Del Potro has the game to win Paris, but him withdrawing from the Asian swing is probably an indication of where his focus is right now: the Davis Cup in December (played on clay).
As much as I would love to see Del Potro there, his chances are bleak after skipping the Asian swing.
Djokovic, Nadal, Murray, Federer and Ferrer with Tsonga, Fish and Berdych does look like a darn good field though, and even if one were to be replaced by Simon or Tipsarevic (or a surprise), the tournament wouldn't suffer.