'It's not impossible': Roger Federer drops massive hint about retirement plans

Roger Federer credits family bliss for his extraordinary longevity after revealing he may play into his 40s after qualifying for a mind-boggling 56th grand slam quarter-final.

Federer, who turned 38 last month, clubbed David Goffin 6-2 6-2 6-0 in little more than an hour to reach the US Open last eight for the 13th time, then declared retirement was nowhere in sight.

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"It's not impossible," the ageless superstar said when asked by Swiss media if he'd still be on tour when he was 40.

"A few years ago, I wouldn't have thought that could be possible. But when you feel fully fit like I do right now, you think you can play forever.

"I see it as a privilege to feel like that for a longer period of time. I haven't had any major setbacks since I felt my back in Montreal against Sascha Zverev (in 2017).

"I had a few little things, but nothing career-threatening. If I feel like that, I can play more freely, concentrate on my tactics and enjoy my off days much more."

Federer thanks family and friends

Federer, who routinely takes his four children to all four majors, says there no reason why and the likes of soon-to-be 38-year-old marvel Serena Williams can't continue chasing slams for years to come.

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"You need to love what you're doing, find a way to really keep yourself entertained because you go through moments where maybe being away from your home city, village, country, house, whatever it may be, friends, it's not that fulfilling," said the world No.3.

"You've sometimes got to look for ways to keep going. I think what's helped me so much is stability with my relationship with my wife, my relationship with my sister and my parents.

"Then just the friends we were able to keep throughout my career on the road. It didn't make me feel like if ever I came home I had nobody.

"I always felt like our friends couldn't wait to come either meet us at the tournaments or wait for us at home. That just made time away or at home so much fun. That has helped me a lot.

"Maybe travelling and only winning 50 per cent of the matches on tour, then maybe also we wouldn't be playing any more.

"But because we know we can still beat the best, win the biggest tournaments, it's so worthwhile to stay there and see if you can go back to these emotions, see if you can do it at a later stage in your career.

"It's quite exciting actually."

Chasing a sixth title in New York, Federer faces Grigor Dimitrov in the quarter-finals on Tuesday.