London (AFP) - Rafael Nadal and Roger Federer headline an eight-man field at the ATP Finals in London that features the top players of 2017 but has a lopsided look to it with no Novak Djokovic or Andy Murray.
Also missing from the field are a host of other top names including Stan Wawrinka and Kei Nishikori, giving the likes of Alexander Zverev the chance to establish themselves at the top of the men's game.
AFP Sport profiles the eight players taking part in the season-ending showpiece.
1) Rafael Nadal Age: 31 World ranking: 1
Nadal has enjoyed an impressive resurgence this year, winning the French Open and US Open before clinching the year-end No. 1 ranking for the fourth time.
The Spaniard, who also reached the Australian Open final, which he lost to Federer, has won a total of six titles in 2017 after bouncing back from an injury-plagued 2016 season.
2) Roger Federer Age: 36 World ranking: 2
Federer has enjoyed a season that must have surpassed even his own wildest expectations, losing just four matches all year.
The Swiss maestro stunned the tennis world by winning the Australian Open early in the year after returning from a long layoff and went on to lift a record eighth Wimbledon crown.
Federer is gunning for a seventh Tour Finals title and an eighth of a stellar year in which he has even mastered long-time nemesis Nadal, winning all four of their clashes.
3) Alexander Zverev Age: 20 World ranking: 3
Tipped as one of the brightest lights among the new generation of tennis stars, Germany's Zverev has enjoyed a breakthrough season, winning five titles including two Masters series trophies.
The highlight of his year was a straight-sets victory against Federer in the final of the Rogers Cup in Montreal, though he has disappointed at the Grand Slams.
4) Dominic Thiem Age: 24 World ranking: 4
Austria's Thiem has long been tipped for great things but has had a relatively disappointing 2017 season with just one title after four tournament victories last year.
The highlight of his Grand Slam year was a run to the semi-finals at Roland Garros, where he was crushed by eventual winner Nadal.
5) Marin Cilic Age: 29 World ranking: 5
The towering Croat, who won the US Open in 2014, reached the second Grand Slam final of his career at Wimbledon but folded spectacularly against Federer.
Cilic's one trophy of the year came in Istanbul, where he defeated Milos Raonic.
He has been affected by injury, missing the Montreal and Cincinnati Masters events but will be dangerous on the indoor hard courts at the O2 in London.
6) Grigor Dimitrov Age: 26 World ranking: 6
Bulgaria's Dimitrov has enjoyed the best season of his career, claiming his first Masters title in Cincinnati in August. Dimitrov also reached the Australian Open semi-finals.
Nicknamed "Baby Fed" early in his career for the similarity of style in his game to the Swiss, Dimitrov has at times struggled to live up to the comparison.
7) David Goffin Age: 26 World ranking: 8
Goffin is the first Belgian singles player in the 48-year history of the ATP Finals to qualify for the season finale.
He served as an alternate last year, replacing the injured Gael Monfils in one round-robin match.
Goffin has enjoyed the best season of his career, including back-to-back Tour titles in October in Shenzhen and Tokyo.
8) Jack Sock Age: 25 World ranking: 9
American Sock completed a week to remember in Paris earlier this month, winning his first Masters title and qualifying for the ATP Finals for the first time, forcing him to ditch a golfing holiday.
Entering the Paris event, Sock was 24th in the Race to London.
The win for the new American No. 1 snapped a streak of 69 consecutive Masters titles won by Europeans.