Roger Federer wants 20 Grand Slams before he retires
Federer has returned to action in Toronto after a summer break
Former world number one Roger Federer believes he can win at least 20 Grand Slam titles before he retires.
Asked if he would be happy to add another three to his record total of 16 major wins, he told Radio 5 live: "No, I wouldn't, I would want to win more.
"Having won three Grand Slams per season three times, and two per year a couple of times, it's something that I think is very do-able for me."
Federer's next opportunity to add to his major wins is at the US Open.
This year's Wimbledon saw Federer fail to reach the final for the first time since 2002 as he lost in the quarter-finals to eventual runner-up Tomas Berdych.
And although the 29-year-old Swiss admitted he is increasingly feeling the stresses and strains of playing, speaking in the build-up to the US Open, which starts on 30 August, he said he still had plenty of motivation to carry on playing for a while yet - in tournaments of all kind.
"At times I was one or two sets away from winning the calendar-year Grand Slam so obviously I feel that I have a great potential in Grand Slam play. But then again Grand Slams are not everything," he said.
"I'm giving 100% for each and every tournament that I play because I don't play a ton of tournaments I only play 16-20 per year, so I'm not over-playing, and that keeps the fire burning.
"Tournaments like Toronto this week and Cincinnati next week are important to me, too. The motivation is huge for the next few years and obviously if I can win Grand Slams that's fantastic, but they are not the only motivation over the next few years."
Federer admitted he did not watch this year's Wimbledon final, as there was not a television where he was on holiday with his family, but said he did not feel any great sense of loss at missing out on the final.
"When you have disappointing losses or a tournament ends early for you, you move on with your life. You don't think 'shouldn't I be at Wimbledon in the finals?', you kind of enjoy the moment with your family, with your friends, just being away from it all," he said.
"That's what I do very well. I switch off very quickly, I don't think of tennis that much when I'm away from the courts, even though subconsciously I have to because I'm a professional and I want to do really well in the long run in tennis.
"So, that was kind of nice [to be away]. Then again, I started to miss tennis as well so I was happy to get back on the practice courts, too."
After his Wimbledon defeat by Berdych, Federer complained of back and leg "issues".
But rejuvenated by a holiday and refreshed by two weeks working with new coach Paul Annacone, he said he felt "perfect" ahead of his return to action in Toronto this week, as he starts his build up to trying to win a sixth US Open title.
And he said with age comes a better understanding of how to get the best out of his body.
"Being a teenager is different to being 23, and being 23 is very different to say being 28. Today, I know my body better than ever," he stated.
"Some things take a little bit longer [to recover from] with age but I can prevent more problems by doing a lot more stretching, physical work, practice, massages. I'm doing everything much more professionally today than I ever have before.
"That's the advantage [of being older], but then of course there's no denying that I've played almost a thousand matches in my life and that obviously has a big wear and tear on your body, too, so you have to be a little bit more careful."
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