|ATP World Tour Finals|
|Venue: O2 Arena, London Dates: 11-18 November|
|Coverage: Follow live coverage across BBC TV, radio, the BBC Sport website & mobile app. Live text commentary available on selected matches.|
Novak Djokovic says his return to world number one seems "unreal" as he looks to cap a remarkable renaissance with victory at the ATP Finals in London.
Djokovic, 31, is the heavy favourite to win the season finale for a sixth time.
The Serb, who dropped out of the world's top 20 in May, plays American John Isner on Monday at 20:00 GMT.
"It took a bit of time for me to find my confidence and level of tennis that I was looking for and working hard for," he said.
Djokovic returned from elbow surgery earlier this year to win Wimbledon and the US Open before reclaiming the world number one spot from Rafael Nadal earlier this month.
With Nadal and Juan Martin del Potro ruled out of the ATP Finals through injury, and Federer losing his opener against Kei Nishikori, Djokovic is deemed the man to beat.
"It has been an amazing season, especially the last five or six months," Djokovic said.
"Everything seems a bit unreal, to be honest. This is really a dream come true."
Germany's world number four Alexander Zverev plays Croatia's Marin Cilic in the afternoon session on Monday (around 14:00 GMT) before Djokovic's starts his bid against Isner.
BBC Sport will have comprehensive, live coverage of the tournament across television, radio and online.
Novak Djokovic (Serbia)
World ranking: 1
2018 highlights: Winning Wimbledon and US Open titles, returning to world number one.
Previous ATP Finals appearances: 10 (champion 2008, 2012, 2013, 2014, 2015)
What he says: "Returning to number one is extra special this year because of the journey I've been through in the last 15 months. It turned to out to be a perfect five months of the year, with two Grand Slam titles."
it looked quite improbable that I would be in this position as the year-end number one, not just because of the rankings -- I was 22 (in May) -- but just because of how I felt on the court, how I was playing.
Alexander Zverev (Germany)
World ranking: 5
2018 highlights: Winning Madrid Open for his third ATP Masters 1000 title, reaching maiden Grand Slam quarter-final.
Previous ATP Finals appearances: 1 (group stage 2017)
What he says: "My shoulder injury is getting better every day and I'm hoping I'll be prepared for London. The year has been very positive. I've won a Masters and made a few other finals, it has been a good year and in the clay-court season I was one of the best players."
Marin Cilic (Croatia)
World ranking: 7
2018 highlights: Reaching Australian Open final, achieving career-high rank of third, winning Queen's.
Previous ATP Finals appearances: 3 (group stage 2014, 2015, 2017)
What he says: "It was an amazing run to the Australian Open final, one of the best moments of my career. I've had a tough time here in London, but there is not much that differentiates the players here. Hopefully this year it can change and I will do well."
John Isner (United States)
World ranking: 10
2018 highlights: Reached first Grand Slam semi-final at Wimbledon, won first Masters 1000 title in Miami.
Previous ATP Finals appearances: Debut
What he says: "Making my debut at this event means a lot to me. It is one that I've been close to making in the past, coming down to the Paris Masters, but I haven't been able to clear that hurdle. So to be here in 2018, at 33, it is a nice feather in my cap. I feel I've earned my spot here but also I know I'm fortunate to be here, with Rafael Nadal and Juan Martin del Potro pulling out."
Roger Federer (Switzerland)
World ranking: 3
2018 highlights: Winning 20th Grand Slam with Australian Open victory, returning to the top of the rankings.
Previous ATP Finals appearances: 15 (champion 2003, 2004, 2006, 2007, 2010, 2011)
What he says: "I'm very happy how this season went, I won another Grand Slam and stayed pretty much injury free. But the tricky part - because I'm not playing as much as I used to in my prime - is finding the rhythm as quick as I have to."
Kevin Anderson (South Africa)
World ranking: 6
2018 highlights: Reaching Wimbledon final after epic semi-final win against Isner, climbing to career-high fifth in the world.
Previous ATP Finals appearances: Debut
What he says: "Reaching the tour finals for the first time was one of my primary goals this year. I feel I've been playing great tennis and if I keep going then I can have a chance of a successful result."
Dominic Thiem (Austria)
World ranking: 8
2018 highlights: Reaching first Grand Slam final at the French Open, also finishing runner-up in Madrid.
Previous ATP Finals appearances: 2 (group stage 2016, 2017)
What he says: "It has been a great year, the beginning was my big goal to come here and that's what I've reached. And also because of my performances in Grand Slams I'm very happy."
Kei Nishikori (Japan)
World ranking: 9
2018 highlights: Reached US Open semi-finals, runner-up in Monte Carlo Masters.
Previous ATP Finals appearances: 3 (semi-finals 2014, 2016)
What he says: "I felt the finals might be beyond me, especially because of the injuries I had at the start of the year. I didn't have any confidence I'd be in the top 10. It took a while to play good tennis but in the last couple of months I have played really well."
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For the fourth time in seven years, Rafael Nadal will not be playing.
The French Open champion finished second in the Race to London rankings, but pulled out of the event earlier this week after having surgery on an ankle injury.
World number four Juan Martin del Potro was also forced to withdraw with the right knee injury he sustained in Shanghai last month.
Britain's Andy Murray and defending champion Grigor Dimitrov are other star names that will be missing.
Murray, who won the event in 2016, remains in the early stages of his comeback following hip surgery, while Bulgaria's Dimitrov did not qualify after a poor second half of the season.
How does the tournament work?
The finals are the culmination of the ATP season and the singles title is contested by the eight players who have accumulated the most ranking points from 52 tournaments - including the four Grand Slams - over the year.
The eight singles players are seeded in terms of points accrued and split into two groups of four.
The groups are played in a round-robin format over the course of the week, with the top two players in each qualifying for the semi-finals on Saturday, 17 November.
The winners meet in the final on Sunday, 18 November at 18:00 GMT.
How can you follow it on the BBC?
On television, Sue Barker will present with Andrew Castle and Tim Henman providing commentary. Three-time tour finals champion Boris Becker will join them on the final weekend.
BBC tennis correspondent Russell Fuller leads the 5 live and 5 live sports extra coverage from London, which you can also listen to online.
The BBC Sport website and app will have daily live text commentaries, plus reports and analysis of every match.