In the chase for the No. 1 world ranking to end the 2014 tennis season, Roger Federer will need to get by with a little help from his friend.

Federer kept his slim hopes for surpassing Novak Djokovic for the top ranking on Tuesday by stopping U.S. Open finalist Kei Nishikori 6-3, 6-2 on Tuesday at the ATP World Finals Tour to move his record to 2-0 in Group B Pool Play.

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He is almost assured a spot in the semifinals even if he loses to Andy Murray in the final match of their group play.

But a Murray win on Thursday would wipe out any hopes Federer has of overtaking Djokovic. Federer also has to hope that Djokovic loses one of his matches in Group A pool play. After disposing of U.S. Open champion Martin Cilic in the first round, Djokovic faces Federer's compatriot, Stanislas Wawrinka on Wednesday.

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Djokovic must lose a match in pool play for Federer to remain in contention for No. 1.

SI.com broke down the scenarios.

"- If (Djokovic) reaches the (semifinal) with a 3-0 (round-robin) record, he will be guaranteed No. 1 regardless of Federer's results in London and the Davis Cup final.

- If Djokovic goes 2-1 in RR play and does not progress beyond the SF, Federer will need to win the title undefeated (5-0) and win one live singles rubber in the Davis Cup final.

- Federer could earn a maximum 225 points in the Davis Cup final (Djokovic drops 150 points from last year's Davis Cup)."

A Wawrinka win over Nole could put a bit more control in Federer's hands. If Federer were to beat Murray and Wawrinka were to end up the Group A pool champion, that would force Djokovic to face Federer in the semifinals - as long as Djokovic handles Tomas Berdych in their final pool-play match.

Federer would finish 3-0 in his group pool play if he can beat Murray and build confidence. Then he'd have to channel his Wimbledon disappointment against Djokovic to return the favor.

Do you think Roger Federer has a shot at taking the No. 1 title away from Novak Djokovic? Comment below or tell us @SportsWN.