It's no secret that the resurgence of Rafael Nadal and Roger Federer has stolen the headlines on the ATP World Tour this year. Big title after big title was theirs to seize and the duo would be rewarded with the top two spots in the year-end Emirates ATP Rankings.

While Nadal will finish the season ahead of Federer at No. 1, the battle for the top position is far from finished. Should the Swiss lift the trophy at this week's Nitto ATP Finals, the gap between the two legends would be a mere 140 points in the Emirates ATP Rankings, as the calendar flips to 2018. That is, just 140 points that separate Federer from adding to his record 302 weeks at World No. 1.

The top spot is within reach, but while the Swiss admits it would be an incredible achievement, he is staying realistic.

"It is interesting," Federer said following a three-set win over Marin Cilic to close out a perfect run through Group Boris Becker. "It's the ultimate achievement in tennis. It always has been for me. But at this age, it just can't be because I think I'll make mistakes if I start chasing it.

"I'm not sure how much the body allows me to chase goals like this. Maybe if I start thinking about it too often and too much, I think I'm maybe also not playing the way I'm supposed to be playing, maybe I tense up, maybe I'm nervous, maybe that's not good for my back. Who knows what it is.

"I have 2,000 points to defend in Australia, [Nadal] doesn't. So there's the problem already. I know he has a lot of points to defend, too, in Australia, but not as many as me. That's why I always said, look, it's not a realistic goal in some ways. I still need to win this tournament before it's actually really close. The year played out the way it did and Rafa was better. He deserves to be there. I'm really happy for him because he had a rough season as well in '16. It's great for him."

Nadal might have had a better season, as Federer admits, but at age 36, the Swiss has enjoyed a renaissance of his own. The Comeback Player of the Year in the 2017 ATP World Tour Awards Presented By Moët & Chandon, he rebounded brilliantly after concluding his 2016 campaign at No. 16 in the Emirates ATP Rankings, due to injury.

In an effort to minimize fatigue and strain on his body, Federer managed his schedule to perfection. He has suffered just four defeats from 56 matches, two of which came after holding match points. While the Basel native laments those losses to Evgeny Donskoy in Dubai and Tommy Haas in Stuttgart, he says there are no regrets following such a successful campaign.

"Regrets, I don't have any," Federer added. "But maybe losing to Haas and Donskoy ended up haunting me. I had match points in both matches. It's not like I didn't try. If I miss out because of that for World No. 1, then maybe I was unlucky. But I also did win matches in Miami, saving match points against Berdych, other matches throughout the season that could have been gone either way as well. In Australia, it was Nishikori. You name it. Things could have turned very quickly much earlier.

"So I'm just happy I'm playing a great season. I'm so happy that I was able to reach this level of play and still being able to play also at the end of the year. It wasn't just one tournament at the beginning, then nothing after that. So it was throughout that I've had a great year."

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Federer reached the 95-title milestone in a season that saw him lift seven trophies, including a pair of Grand Slam victories at the Australian Open and Wimbledon, as well as ATP World Tour Masters 1000 crowns in Indian Wells, Miami and Shanghai. With an unprecedented seventh title at the Nitto ATP Finals just two wins away, Federer believes there is plenty to be grateful for.

"I totally over-exceeded my expectations. I'm just happy I'm injury-free and healthy right now and still enjoying myself. In Australia, I hope to be fit again, to walk out on Rod Laver Arena and hopefully defend my title. But we're still very far away at this point."

But before Federer turns his attention to 2018, he has one last matter of business to attend to in London. The Swiss will next face the winner of Friday's round-robin clash between Dominic Thiem and David Goffin, with a spot in the final at stake.