Federer has endured a dismal campaign marred by a series of shock defeats and the 17-time Grand Slam champion was unable to finish on a high note as world number one Nadal sent him crashing out of the season-ending event with a 7-5, 6-3 victory on Sunday.
After reigning over men's tennis for the best part of a decade, the 32-year-old is undeniably a fading force, prompting some to suggest he may consider hanging up his racquet to focus on life as a father of twin daughters.
But Federer is adamant that is not an option just yet because his love of the sport remains too strong.
"For me, it's pretty simple: this is what I used to do as a little boy,” said Federer. “It's something that always is there in your DNA.
"Clearly today it's different than when I was 12 years old, but it's just something I enjoy doing.
"The thing is that when you stop, you're still so young that why stop so early? Why just walk away from it because I have many other things to do in my life than play tennis, but because I can still choose, I pick to play.
"As long as I have this choice, I'll keep on playing."
Federer, troubled by a back injury in the first-half of the campaign, claims his lack of success over the last 11 months is more down to his body failing him than a lack of hunger.
"Considering the back issues I've had, I'm pleased that I'm pain-free for a long period of time now with a lot of tennis," he said.
"That's definitely going to give me confidence physically and mentally.
"Just beating two top-10 players recently [Richard Gasquet, Juan Martin del Potro] is a good thing for me after not having beaten any for almost seven or eight months."
Federer’s ranking has slumped to seventh in the world — his lowest placing for 11 years, but he is confident of starting again next year.
"I'm back confident and excited going into the off-season and starting again next year.
"The rankings are secondary for me. I need to make sure I stay competitive and can hang with the best.”
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