Defending champion Novak Djokovic and tournament rookie Dominic Thiem kick off the ATP World Tour Finals with the opening round robin match at The O2 Arena in London.
Where to watch
Djokovic vs Thiem starts at 2pm GMT and is live on Sky Sports 3HD, BBC2 HD and BBC Radio Five Live sports extra.
Novak Djokovic begins attempts to wrestle back world number one from Andy Murray when he takes on Dominic Thiem in the opening match of the ATP World Tour Finals at The O2 Arena in London. The Serbian was replaced by Murray at the Paris Masters but knows a record fifth title in a row at the season-ending tour finals will likely be sufficient to take his place at the top of the standings.
Victory in the English capital will see Djokovic draw level with Roger Federer and claim a sixth title, and he could not have asked for a better draw as he chases history. The 12-time grand slam faces Thiem, Gael Monfils and Milos Raonic in the round robin stage as he attempts to reignite his season which has fallen away since he won the French Open at the start of June.
Djokovic has never lost in a combined 23 meetings with the trio, however defeat in the US Open final to Stanislas Wawrinka and successive quarter-final exits at the last two Masters Series 1000 events in Shanghai and Paris has ruined his reputation as the man to beat in the men's game. He must outperform Murray this week to ensure he ends the year as world number one for a fifth time.
Thiem meanwhile may have benefitted from injury to Rafael Nadal which allows him to take his place in his first ever ATP Finals, yet there is no doubt the Austrian has qualified on merit. The 23-year-old reached the last four at Roland Garros, losing to Djokovic in straight sets, and has twice reached the last eight in the Masters Series events in Rome and Cincinnati.
Yet despite having been one of the standout performers of the year, Thiem has enjoyed minimal success against Djokovic having lost all three of their meetings without winning a set. Victory on the french clay earlier in the year was among Djokovic's most routine of the season and he will be bidding for a similar performance to kick his campaign back into gear.
What the players say
Novak Djokovic: "I have plenty of motivation, [and] it starts from within. Even after 10-plus years at a professional level, I still feel I have a lot of gas in my tank. I feel like I still have a lot more years ahead of me. I feel great joy when I compete, when I play.
"The power of passion towards the sport is the No. 1 thing that drives me to play, to enjoy to play. This is the game. If you don't enjoy the game—your time on court—everything else becomes two or three, five times more difficult than it is or should be.
"[Murray's] definitely a well-deserved No. 1 at this point. Whether or not he can sustain it is not a question for me ... The qualities he possesses as a player, his determination to the sport, there's a good chance that he can still play in this level for some time."
Dominic Thiem: "In 2014, it was difficult for me to have a decent off-season, but last year I watched it and thought the [Barclays ATP World Tour] Finals was so difficult to amass so many [Emirates ATP Rankings] points, to compile so many good results. So to have qualified is a big dream.
"I had a very good off season in 2015, then my body got a lot better. I think that was very important, and I kept improving my game on the faster surfaces. The first half of the year was really great.
"I want to develop my game and compete for the really big titles. I still have to prove myself in the big tournaments, I am still far off from it. But not too far. The tough times come when you exit tournaments early, or if you don't practise well. The key is to be patient."
Betting odds (source Betfair):
Novak Djokovic 1/6 vs 5/1 Dominic Thiem
Head-to-head record: Djokovic 3-0 Thiem. Last match French Open (clay) Djokovic bt Thiem 6-2 6-1 6-4
Previous meetings at the ATP World Tour Finals: N/A