With just the Paris Masters left before the ATP World Tour Finals begins, the qualification process for the London showpiece has almost been completed.
The tournament is open to the top eight players in the world but as home favourite Andy Murray has had to withdraw through injury, the ninth-ranked player in the 'Race to London' will be also be present this year.
Points are accumulated through the year, with the grand slams (2,000 points for winning) being the most lucrative ahead of the nine Masters series events (1,000 points for a win) and the third- (500 points) and fourth-tier (250 points) tournaments.
Five positions have already been decided and there is a tight battle underway for the final three places.
They only chance of a British participant comes in the doubles, but as it stands no player from the host nation will be able to compete.
Here we take a look at who has made it and who is still fighting for a seat at the table.
Singles - already qualified
Nadal was still out of action due to a knee injury at the start of the year, but soon after his return it became clear he would easily gain enough points to qualify. Before he even had the chance to take his obligatory victory at the French Open he had already took 1,000 points at each of the Masters tournaments in Indian Wells, Madrid and Rome. After Roland Garros yielded another 2,000 he was well on his way, picking up wins in two more Masters events and the US Open for good measure.
The Serbian started his year by taking maximum points at the Australian Open, which he followed with a win at a 500 event in Dubai and, after a shaky patch of form, he took 1,000 points at the Monte Carlo Masters. Big points hauls at Roland Garros, Wimbledon and the US Open were followed by a 500 win in Beijing and a Masters victory in Shanghai, enough to give him the No 2 spot in the race comfortably.
Andy Murray (absent)
The British No 1 was set to be the third seed but has had to pull out after undergoing back surgery. Reaching the final of the Australian Open coupled with his historic win at Wimbledon and victory in the Miami Masters had seen him well up in the race before his form tailed off in the second half of the year.
It is a measure of the top players' dominance in the current era that all the grand slam and Masters 1000 titles so far this year have been Hoovered up by the three highest-ranked men in the race. Ferrer is the best of the rest, racking up points in the first half of the season by reaching the semi-final of the Australian Open and finishing as the runner-up at both the Miami Masters and French Open. The Spanish veteran has found results hard to come by since Roland Garros, although he has reached the final of the 500 tournament in Valencia.
Juan Martin del Potro
Del Potro has not quite lived up to his potential in the grand slams this year, with a semi-final defeat in an epic contest against Novak Djokovic at Wimbledon his best effort. His early qualification for the Finals has been built on two appearances in the final of Masters 1000 events - in Indian Wells and Shanghai - and wins in four of the 500 tournaments: Rotterdam, Washington DC, Tokyo and Basel. No other player has won as many of the third-tier events on the Tour.
The former Wimbledon finalist has not reached the final of a grand slam or Masters 1000 event, or even won an ATP tournament of any description, but his consistency has allowed him to book a spot at the O2 already. He has returned 360 points on six separate occasions, by reaching the quarter-finals of the Australian Open and Wimbledon and the semis of four Masters 1000 events. Other significant points came from reaching the final of the 500 event in Dubai and the 250 tournaments in Marseille and Bangkok.
On the cusp
The Swiss maestro usually qualifies with plenty of time to spare but is being made to sweat it out this time. His year started relatively well as he reached the semi-finals of the Australian Open but he has followed that up with only a lone quarter-final appearance at the grand slam events. His performances in the Masters tournaments have been even worse, although he did bag what now seems a crucial 600 points by reaching the final in Rome. Taking a 250 title in Halle is his only tournament win of the year.
Federer could have clinched qualification if he won the 500 title on home soil in Basel, but he lost in the final to Del Potro. He went into the event almost level with Stanislas Wawrinka, but his compatriot was eliminated in the opening round. Even so, it would take an early exit plus strong runs from a number of other players in Paris to deny him.
Three-way battle for two places?
Runs to the final of Madrid and the semi-finals of the US Open, as well as a win at the Portugal Open, have put the Swiss player on the brink of reaching the year-end championships for the first time. He could have put himself in an even stronger position with a good run at Basel, but the fourth seed suffered a shock loss to Edouard Roger-Vasselin in the opening round. Another shock exit in Paris could give Wawrinka some trouble.
A semi-final appearance at the US Open and three separate wins in 250 events have given Gasquet a real chance of returning to the season finale for the first time since 2007. A run to the final of the Madrid Masters also helped his chances, but he could still miss out.
Gasquet and Tsonga are scheduled to meet in the third round of the Paris Masters, a match which could serve as a straight eliminator. The difference between a quarter-final exit and a third-round exit is 90 points, while the difference between the two players is 65 points.
It is still possible for both Gasquet and Tsonga to qualify for the Finals, but they need Wawrinka to lose his Paris opener against Feliciano Lopez or a qualifier. If he does come through it, and Federer also qualifies as expected, then it is likely down to a straight fight between the Frenchmen.
If he does not make it, Tsonga is sure to look back on his injury-enforced absence from the latter stages of Wimbledon and the whole of the subsequent North American hard court swing with an even greater sense of regret. Tsonga, who reached the semi-finals of the French Open, missed out a huge amount of points when he was forced to sit out the Montreal and Cincinnati Masters as well as the US Open.
Milos Raonic, Tommy Haas and Nicolas Almagro are still in with a mathematical chance of reaching the London event. The best-placed of the trio is Raonic, who reached the final of the Masters event in Montreal. Another runner-up finish in Paris could allow him to qualify, but he would need two out of Wawrinka, Gasquet and Tsonga to go out by the quarter-finals.
Haas and Almagro languish further behind and need to win the Paris Masters to stand any chance of qualifying.
With Andy Murray having to pull out, attention turned to the doubles qualification race for potential British interest. Andy's brother Jamie Murray is currently the highest-ranked Brit, lying in 10th place along with his Australian partner John Peers. They are currently 375 points behind the eighth-ranked pair, meaning a win at the Paris Masters would see them qualify automatically. They have won three tournaments already this year, although they were all 250 events.
If they finish as runners-up, Polish duo Mariusz Fyrstenberg and Marcin Matkowski need to reach the quarter-finals to deny them, but as they are poised to face Bryan brothers Bob and Mike in the second round, that is no easy task. Anything less than the final will not do for Murray and Peers.
Another Brit in with an outside shot is Dominic Inglot, who caused a shock by winning the recent 500 event in Valencia alongside Filipino Treat Huey. Again, they need to reach the Paris Masters final to have any chance and, as long as Fyrstenberg and Matkowski don't finish as runners-up, a victory in the tournament will ensure qualification.
They could also make it by losing in the final if the Polish pair are beaten by the Bryans. As Murray and Inglot are on the same side of the draw, they cannot both qualify.
The Bryans are the top-qualifying doubles team having racked up over twice the points of their nearest challengers - Alexander Peya and Bruno Soares - by winning three of the four grand slams and four of the eight Masters series events so far.