Both Federer and Nadal have shared the Grand Slam titles this year with the latter winning at the French Open and US Open and the former victorious in Australia and Wimbledon.
It has been an incredible rise back to the top of the game after both players struggled with injury woes over the past few years.
Novak Djokovic and Andy Murray have shared the limelight with the Briton becoming World No1 at the end of 2016.
But it has been a season ravaged by injuries for Murray while Djokovic also ruled himself out of action for the rest of the year ahead of the US Open.
That’s taking nothing away from the achievements of both Nadal and Federer, who now have 35 Grand Slam titles between them.
The Swiss tennis legend remains on top with 19 but his rival will finish 2017 at the summit of the world rankings with one win at the Paris Masters.
And Federer admits he regrets not making it a closer battle with Nadal for the year-end No1 spot.
“Ever since Rafa won the US Open, I knew it was going to be very, very difficult,” Federer told The Wall Street Journal.
“I wish I could have chased [No. 1] more — my only regret is that I couldn’t have chased it more at Cincinnati and the US Open.
“That was a pity — but Rafa played a full schedule, and he deserves it. I’m OK with that.”