New Delhi: Novak Djokovic emerged as the undisputed king of tennis in 2015.
Sweeping three out of four majors, the Serb was the most dominant athlete in world sport this year.
However, the legendary Roger Federer deserves a special mention for pushing Nole all the way in 2015.
Despite battling age, the Swiss maestro outperformed most of his younger rivals like Rafael Nadal and Andy Murray.
In a gripping sub-plot to the new Grand Slam season, Federer and Djokovic are now in a race to become the first USD 100 million men in tennis in 2016.
No player in the history of the sport has broken through the USD 100 million on-court earnings barrier but world number one Djokovic and Federer, the number three, should reach the landmark next year.
Djokovic, 28, has just over USD 94 million in prize money while Federer, six years the Serb's senior, has banked USD 97.3 million.
With USD 3.85 million on offer for the winner of January's Australian Open, the season's first major, the veteran Swiss would be the first man to the magical number even if the odds are heavily stacked against a player who won the last of his 17 Grand Slam titles in 2012.
The staggering rewards for the modern player, all boosted by lucrative off-court earnings through sponsorship and endorsements, are a far cry from the heavyweights of the sport who starred in earlier eras.
Rod Laver, the last man to complete the calendar Grand Slam -- something that eluded Djokovic courtesy of a French Open final loss in 2015 -- ended his playing career with USD 1.5 million, still a huge sum by the standards of the late 1960s.
John McEnroe earned 12.5 million while Federer's hero, Pete Sampras banked 43 million before he retired in 2002.
Djokovic earned a season record 21.5 million in 2015, a year which saw him win three of the four majors -- taking his total to 10 in total.
"My season was the best of my career with many highlights. It inspires me even more to keep on going, and I hope to continue to play at this level in 2016," said Djokovic.
Despite his dominance of the sport, Djokovic still has some catching up to do when it comes to matching Federer's overall personal fortune.
According to Forbes' rich list, Federer was the fifth highest-earning sportsman in 2015 thanks to 58 million in endorsements.
Djokovic was 13th, his on-court wealth boosted by 31 million worth of commercial riches.
But the Serb knows time -- and the form which saw him win 82 matches and suffer just six losses last season -- is on his side.
"I think I have a good chance. I'm 28 and I still don't feel like the end is anytime soon, that definitely excites me and motivates me to keep going."
The staggering wealth in the men's game dwarfs the women's tour.
Serena Williams's on-court earnings stood at just over 74 million after a 2015 season which saw the American also claim three of the the four Grand Slam titles.
Rival Maria Sharapova, the world's richest sportswoman due to her lucrative off-court portfolio, has earned less than half than Williams -- 36.4 million.
Back in the men's game, 14-time major winner Rafael Nadal has banked 75 million on court while current world number two Andy Murray has earned 42.5 million.
(With AFP inputs)