Rafael Nadal (Ranked No.1) - Champion at the French Open and the US Open, Nadal is guaranteed to finish as the year-end No.1 for the fourth time in his career.
Roger Federer (Ranked No. 2) - The Swiss legend has won the Australian Open and Wimbledon this year, and is a six-time winner of the World Tour Finals.
Alexander Zverev (Ranked No.3) - German 20-year-old Zverev has broken into the big time this year with Masters Series victories in Rome and Montreal.
Dominic Thiem (Ranked No.4) - The Austrian enjoyed a superb clay-court campaign, including a win over Nadal, before fading in the second half of the season.
Marin Cilic (Ranked No.5) - A finalist at Wimbledon, Cilic has had another consistent season.
Grigor Dimitrov (Ranked No.6) - The Bulgarian reached the semi-finals of the Australian Open and won the Cincinnati Masters.
David Goffin (Ranked No.8) - The highlight of a solid year was his victory at the Japan Open.
Jack Sock (Ranked No.9) - Sock came from nowhere to qualify for the O2 with his shock victory at the Paris Masters.
*Stan Wawrinka (ranked No.7) is absent due to injury.
Roger Federer is the strong favourite with the bookies and could perhaps challenge for this title with his eyes closed. In the absence of the injured Novak Djokovic, Andy Murray and Stan Wawrinka, and with the in-form Juan Martin del Potro narrowly missing out on qualification, there does not appear to be anyone in this line-up capable of stopping him. For all his success in 2017, Rafael Nadal has lost all four of his meetings with Federer this year, he picked up an injury in Paris and his record at the O2 is very disappointing.
Of the rest, Jack Sock is the only one who could be described as being in top form after winning in Paris, but he was helped by the drawing opening up for him. Dominic Thiem always seems to blow a gasket halfway through the season, Alexander Zverev has suffered some early exits in recent tournaments and David Goffin will be bringing a knife to a gunfight in terms of his relative lack of power compared to the rest of the players.
Federer should and probably will win if fully fit, but any punters looking for value might want to consider an each-way bet on either Marin Cilic or Grigor Dimitrov. Cilic has been steady over the past couple of months and will certainly be eyeing up a semi-final spot, while Dimitrov could perhaps go even further on his O2 debut. The Bulgarian reached the quarter-finals in Shanghai and the final in Stockholm just last month, he has a good all-court game which should be suited to the fast indoor surface and can be backed at attractive odds of around 10/1.
Sports.net’s Top Tip
*Please note, odds may fluctuate.