The ATP Finals starts in London on Sunday and two players have dominated the talk in the build-up to the season-ending event.
New world number one Novak Djokovic and 20-time Grand Slam champion Roger Federer are among the players set to do battle at the O2 in an event dubbed the fifth Major.
Djokovic and Federer were joined by Alexander Zverev, Kevin Anderson, Marin Cilic and Dominic Thiem in qualifying automatically for the tournament after finishing in the top eight of the rankings.
Kei Nishikori and John Isner, meanwhile, made the cut after the injured Rafael Nadal and Juan Martin del Potro were forced to withdraw.
Djokovic, who has won the last two Grand Slams, is the favourite to win the tournament. Doing so would see the Serb clinch his fifth ATP Finals victory.
Federer, rated as one of the best players in history, will be determined to deny his rival another triumph, however, and end a mixed season on a high.
But is it simply a two-horse race? Here, we take a closer look at the players hoping to produce an upset in London.
Group Guga Kuerten
Career titles: 9
Best Grand Slam result: French Open, QF
ATP Finals record: 1-2
As one of the most highly-rated young players in the world, Zverev is no stranger to hype.
The 21-year-old has been described as a future Grand Slam winner for the past two years and he is quickly catching up with the likes of Nishikori and Thiem for the number of career titles won.
Perhaps it is about time the German properly announced himself on a big stage. Considering his ability and form in ATP Tour events, it is a surprise that he has only reached the quarter-finals of a Major once, at the French.
His moment at the Slams will undoubtedly come but Zverev can make a statement in London this week, against the sports elite.
Having reached the semi-finals in Shanghai and Basel just last month, Zverev then made the quarter-finals of the Paris Masters where he lost to eventual champion Karen Khachanov.
On the face of it, fans of Zverev should be feeling optimistic of a promising runs at the O2, but his chances may well rest on the severity of a shoulder injury he has been nursing for a number of weeks.
Career titles: 18
Best Grand Slam result: US Open, W
ATP Finals record: 1-8
At the age of 30, Cilic has seen and done it all. Aside from Federer and Djokovic, he is the most experienced, respected and accomplished player in the line-up.
And yet Cilic and the ATP Finals is a combination that rarely produces success.
In three appearances at the season-ending tournament, the Croat giant has managed to win just one of his nine matches, suffering defeats to the likes of Andy Murray, Tomas Berdych and Jack Sock. Will this be a factor this week? Perhaps.
But a more legitimate concern is Cilics overall form. Since reaching the quarter-finals at Flushing Meadows, he has endured a difficult period, losing five of his eight matches.
He took a set off Djokovic in Paris but that only seemed to awaken the Serbian great, who proceeded to win the match in fine style.
The draw appears to have worked out in Cilics favour, at least, and he will back himself to defeat the inexperienced Zverev – particularly if he is hampered by injury – and the dangerous but flawed Isner.
Career titles: 14
Best Grand Slam result: Wimbledon, SF
ATP Finals record: 0-0
While Rafael Nadals withdrawal was a significant blow to the tournament and the Spaniard himself, it has at least opened the door to Isner.
The big-serving American was resigned to missing out on the tournament despite an impressive season, but snuck in after Nadal confirmed he required ankle surgery.
Known for his mammoth serve, which has produced almost 11,000 aces, Isner has shown he has more to his game this season in superb runs at Wimbledon and the US Open.
During his entire career, Isner has won 92% of his service games and will expect his serve to be in deadly form in indoor conditions.
The 33-year-old will naturally be incredibly difficult to break and he certainly could snatch a couple of surprise victories in tie-breaks.
Isners problem is that he generally finds himself outclassed when coming up against fellow top players and some of the best returners in the game will be standing on the other side of the court in London.
Group Lleyton Hewitt
Nationality: South African
Career titles: 5
Best Grand Slam result: Wimbledon & US Open, F
ATP Finals record: 0-0
No player in this years line-up has won less titles in their career than Anderson, but that does not mean the South African should be discounted.
In fact, there is enough evidence to suggest Anderson could well progress to the knockout stages.
The late bloomer from Johannesburg has been in fine form over the past 18 months, reaching two Grand Slam finals and securing memorable victories over the likes of Federer and Andy Murray.
Beating Federer at this years Wimbledon was particularly impressive, with Anderson saving match point before mounting an impressive and ultimately successful comeback.
He was thrashed by Djokovic in a heavily one-sided final, but this was more or less expected after his marathon semi-final meeting with Isner.
Anderson possesses one of the finest serves in the sport but, crucially, has proved he has the overall game to trouble anyone.
Career titles: 11
Best Grand Slam result: French Open, F
ATP Finals record: 2-4
Often described as a clay-court specialist, Thiem is determined to show he is more than a one-trick pony.
Having reached back-to-back semi-finals at the French Open, Thiem went one better this year, finishing as runners-up as Rafael Nadal won his 11th title at the venue.
Despite being earmarked as a future Grand Slam champion, the 25-year-old has generally disappointed on hard, indoor courts.
But perhaps recent results show Thiem is finally about to fulfil his true potential and announce himself as a great all-rounder player.
Flushing Meadows had not been a happy hunting ground for the Austrian but he enjoyed a promising run to the quarter-finals this year.
A shock defeat of Nadal appeared to be on the cards after Thiem took the opening set 6-0, but the then-world number one rallied to win in five sets.
Still, Thiems performance in New York – and his subsequent victory in St Petersburg – suggest he is ready to raise his game outside of his favoured clay-court season.
Career titles: 11
Best Grand Slam result: US Open, F
ATP Finals record: 4-7
In a field of quality yet fairly inexperienced stars, Nishikori surprisingly represents the player with the most experience in ATP Finals events, having played in three tournaments and reached the semi-finals on his last appearance in 2016.
Despite only participating in the event because of Juan Martin del Potros withdrawal, the Japanese sensation is arguably the favourite to progress from this group along with Federer.
To qualify for the tournament is impressive in itself, with the former US Open finalist enduring a disastrous start to the year as he was knocked out of a Challenger event in the first round by world number 238 Dennis Novikov.
Nishikori was plagued by injury problems at the start of the year but made the quarter-finals of Wimbledon and beat Marin Cilic on his way to a US Open semi-final.
He generally finds himself outgunned by the top players but narrow defeats to Federer in Paris and Shanghai recently showed he is capable of competing with the best.