Who will claim tennis' $2.4M jackpot?

"I might as well try and enjoy it because I could lose it at the tour finals and never be there again," Murray told reporters, referring to the year-end championships, which start Sunday in London.

Indeed, Djokovic can regain the top position on Nov. 21 and finish the season as No. 1 for the third straight time with a strong showing at the World Tour Finals.

The 29-year-old has certainly fared well at the O2 Arena, winning a record four consecutive titles and if he makes it five in a row while winning at least two of his round-robin matches, Djokovic is guaranteed to seize back the No. 1 ranking from Murray.

Djokovic, however, has struggled since winning the grand slam he craved, the French Open, in June.

A loss of motivation, personal issues and injuries have slowed the Serb, who became the first man in 47 years to claim four straight majors when he defeated Murray in the final at Roland Garros.

His ties to a "spiritual guru" and former Spanish pro, Pepe Imaz, raised eyebrows, especially since his usual coaches, Boris Becker and Marian Vajda, didn't accompany him at the recently concluded Paris Masters, where Djokovic relinquished the No. 1 ranking.

The mantra of Imaz's "tennis group" in Marbella is: "We truly believe love is the way to live life."

Becker and Vajda are expected to return to the Djokovic camp in London and helping Djokovic is that, seemingly, he drew the easier group in the eight-man tournament, having never lost to group rivals Milos Raonic, Gael Monfils and Dominic Thiem. But then Djokovic had never tasted defeat to Marin Cilic in 14 matches -- before losing to the Croat in the City of Light.

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