Federer will turn 37 this year but has two Grand Slam titles to defend with the first coming at the Australian Open, which starts on January 15.

The Swiss will start the tournament as favourite to retain his crown and add a 20th Grand Slam to his record.

But the tag is as much to do with his rivals’ problems as his own form; Andy Murray and Kei Nishikori have pulled out with injury while Novak Djokovic, Rafael Nadal and Stan Wawrinka all arrive in Australia under a fitness cloud.

And Federer, who took six months off in 2016 to deal with knee and back problems, has revealed that he has learned to box clever in training to avoid further injury.

"When you’re younger you have to put in the hours to be able to tell yourself ‘I can stay out on a court for four hours and train for 10 days straight’,” Federer said after beating Alexander Zverev 6-7, 6-0, 6-2 at the Hopman Cup in Perth.

“You have to prove it to yourself that you can do it. It’s more of a mental thing in my opinion.

“Of course, your game needs a lot of tennis and your game needs fitness so you don’t get hurt so often.

“But as you grow older, it becomes a bit more quality-orientated and not so much quantity because quantity hurts the body.

“I’ve played almost 1500 matches in my career so you have to be careful there.”

Federer is winding down his career by reducing his schedule, last year skipping the clay-court season and playing just 12 tournaments in total.

And a number of former professionals including Mats Wilander have recently backed the 36-year-old to carry on even until he’s 40, something the Swiss has said is only possible if he can balance tennis with family life.

Federer added: “It’s nice because I work part-time now: work in the morning, off in the afternoon or the other way around.

“It’s good doing that, it’s good being a husband, good being a tennis player. 

“I have the best of all worlds. It’s great.”