For the first time since 2003, we end the season with four different men in possession of the four grand slam titles.
With French Open champion Rafael Nadal absent from the ATP World Tour Finals as he continues his recovery from a knee injury which has sidelined him since June, the battle to win the final event of the season appears to be a three-horse race.
Novak Djokovic, who started the year by defending his Australian Open title, is guaranteed to end the year as world No. 1, but with the year-end ranking already in the bag, will that diminish his drive to win the final event of the season?
The bookies certainly don't think so, with the Serb the 2/1 favourite with bet365 to end the season on a high with victory in London.
The stand-out match of the round robin stages is undoubtedly the showdown between Djokovic and Andy Murray, after the pair were both drawn in Group A.
Having met six times already this year, with three wins apiece, the rivalry between the pair - born just a week apart - is finely poised. Djokovic won their last contest in Shanghai, but the home crowd could well give Murray the edge.
In what has been a glorious year for British sport, Murray reached the Wimbledon final for the first time before going on to win Olympic gold in front of his home fans. The Scot to taste victory on home soil again is offered at odds of 9/4 with bet365.
Murray has the second-best indoor record of any current player behind Roger Federer, who was in sizzling form as he won the year-end title for a record sixth time last season.
But the Swiss does not have the same momentum heading to London this year. Twelve months ago he arrived at the O2 Arena on the back of titles in Basel and Paris - this year he suffered a shock defeat at the Swiss Indoors before pulling out of the Paris Masters with an injury niggle.
Cash in with Carter
- Andy Murray to win World Tour Finals - 9/4 at bet365
- Juan Martin Del Potro to reach the final - 9/2 at bet365
Federer's recent form is reflected in his odds of 11/4 and, while he will be relieved to avoid Murray in the group stages, he will have a nervous eye on his group-stage meeting with world No. 8 Juan Martin Del Potro, who denied him a sixth title in the final in Basel last month.
After finally returning to the kind of form which saw him win the US Open title in 2009, Del Potro is making his first appearance in London in three years - when he lost in the final to Nikolay Davydenko. The Argentine will be a massive dark horse and at odds of 9/1 could be worth an each-way bet.
Also in Group B, David Ferrer (22/1) arrives in London in red-hot form following his victory at the Paris Masters, but fatigue could play its part for the Spaniard. Janko Tipsarevic (50/1), an alternate in London last year after Murray pulled out, qualified in his own right this season, but is likely to be out of his depth against the big boys.
Tsonga reached the final last year but has recently suffered back-to-back defeats to Berdych, while the Czech arrives in London on the back of victory in Stockholm recently. Both are potentially dangerous opponents for Murray and Djokovic, but the pair should have enough quality to make it through to the semi-finals.