With just three weeks remaining of the regular ATP Tour season, some of the leading players in the world are chasing a place at the ATP World Tour Finals at London's O2 Arena in November.

Novak Djokovic, Roger Federer and Rafael Nadal are already assured of their spot in the eight-man tournament, while Australian Open champion Stanislas Wawrinka was confirmed for the event yesterday, but seven players remain in the hunt for the four places that are still on offer to the chasing pack in the standings for 2014.

Below, Sports Mole brings you all of the information that you need to know ahead of the tournaments in Moscow, Stockholm and Vienna this week.

5. Kei Nishikori

Points: 4,265

Form: After his outstanding run to the US Open final, Kei Nishikori returned to the ATP Tour to put together a run of nine consecutive victories to win tournaments in both Kuala Lumpur and Tokyo, but the Japanese star suffered a second-round exit at the hands of American Jack Sock at the Shanghai Masters. However, that could perhaps be put down to fatigue, and the 24-year-old has opted to sit out this week.

Next Tournament: Valencia

What's required: Nishikori will take to court in Valencia next week with his rivals a lot closer to him in the Race to London, but the worst-case scenario is that he will still hold an advantage of around 300 points to ninth place. A couple of quarter-final appearances in Valencia and Paris should be enough for the Flushing Meadows runner-up to make the finals.

6. Marin Cilic

Points: 3,990

Form: After winning his maiden Grand Slam title at the US Open, Marin Cilic has struggled to continue that form in the weeks that have followed. He made the quarter-finals in Beijing before losing to Murray, but a first-round exit to Ivo Karlovic in Shanghai will worry the tall Croatian.

Next Tournament: Moscow

What's required: As the only Grand Slam champion still to qualify for the finals, Cilic is in a strong position, and he will be confirmed for London at the end of the week providing that Berdych or Raonic don't win in Stockholm or Moscow this week. Even if he finds himself with work to do in the concluding tournaments, he should comfortably seal his place.

7. Tomas Berdych

Points: 3,945

Form: Tomas Berdych can take a lot of positives from the past two weeks on the ATP Tour. He stormed through to the final in Beijing without dropping a set before being on the receiving end of a shot-perfect performance from Djokovic in the final, while he reached the last eight in Shanghai with his run in the tournament being ended by eventual finalist Gilles Simon.

Next Tournament: Stockholm

What's required: Berdych is in a position where he knows he will hang on to seventh place at the end of the week with a couple of wins in Stockholm, but he is seeded first in Sweden and a tournament victory will see him have one foot into the final. A last-four spot in either Valencia or Paris should also see him confirm his place in London.

8. Milos Raonic

Points: 3,750

Form: Milos Raonic came through some testing encounters to reach the final in Tokyo, but his chance to earn some vital points in Shanghai were scuppered when he was forced to withdraw from his second-round match with Juan Monaco due to illness.

Next Tournament: Moscow

What's required: With just 35 points separating himself from ninth-placed David Ferrer, Raonic needs to perform in Moscow this week to avoid chasing in the closing tournaments. His participation in London could come down to the showings of his main rivals, but a win in Basel or last-four spot in Paris would probably be enough for him to qualify for the O2.

9. David Ferrer

Points: 3,715

Form: Losing his opening matches in Shenzhen and Tokyo seemed to have put David Ferrer on the back foot heading into Shanghai but after dropping down the standings, he went some way to regaining much-needed momentum by reaching the last eight, beating Murray along the way before losing to Djokovic.

Next Tournament: Vienna

What's required: Ferrer is in the same boat as anyone who is outside of the top-eight positions - he needs wins. As the top seed in Vienna, he will be expecting to reach the final to add some vital points but he will need to at least reach the last four in either Valencia or Paris, where he won in 2012, to guarantee his place.

10. Andy Murray

Points: 3,655

Form: A weight was lifted off Andy Murray's shoulders when he won his first tournament since Wimbledon 2013 in beating Tommy Robredo to win in Shenzhen before that was followed up with a semi-final appearance in Beijing. The Scot will be disappointed with his efforts in Shanghai but his exit gave him an extra day of recuperation ahead of his return to Europe.

Next Tournament: Vienna

What's required: Murray is currently 95 points away from eighth place which means that it's imperative that he wins in Vienna this week, which would also deny Ferrer maximum points in Austria. The two-time major champion would have to follow that up with a minimum of a last-four finish in Valencia or Paris to give himself any kind of chance of making London, but with the intention of playing six weeks in a row, it could be a tough ask for the 27-year-old.

11. Grigor Dimitrov

Points: 3,450

Form: Grigor Dimitrov's form during the summer appeared to make him a cert for the finals, but the standard of his performances has dropped off considerably since the US Open. After losing in the last eight in Beijing, he was knocked out in the last 32 in Shanghai by Julien Benneteau.

Next Tournament: Stockholm

What's required: Dimitrov must defend his title in Stockholm this week to give himself any sort of chance for London. Failing that, he must reach the final in either Basel or Paris, or he will have to wait another 12 months to make his debut in the end-of-season tournament.