Men’s tennis has developed into a survival of the fittest, but the game’s most successful senior citizen continues to glide through the years with apparently consummate ease. With the exception of the six months he took off in the second half of 2016 to rest an injured knee, 36-year-old Roger Federer has hardly had an interruption to his remarkable career.

The world No 2’s continuing fitness is all the more remarkable given the struggles of so many of his rivals, particularly those in their thirties. Andy Murray, who has had hip surgery, will be missing when the Australian Open starts here on Monday, Novak Djokovic and Stan Wawrinka have only just confirmed their participation after six months out with elbow and knee problems respectively, and Rafael Nadal goes into the year’s opening Grand Slam tournament without any competitive matches under his belt after a recurrence of his perennial knee problems.

Nadal thinks the sport should investigate the number of injuries suffered by the top players – and indeed the Association of Tennis Professionals is monitoring the situation - but Federer told reporters here: “I guess it’s a little bit normal, not to be always 100 per cent fit and healthy. The moment when top guys are hurt, you guys know about it. It’s not like we can cover it up so easily. There are maybe many other players that are injured right now, but we don’t talk about it because they’re playing on Court 25.

“The ATP is looking into it. From what I heard, there are actually fewer injuries throughout. What is an injury? How bad is an injury? It’s all interpretation, I guess.

“I’ve always said that I guess the moment you reach 30, it’s normal to maybe have some signs of usage of the body, or whatever you want to call it. But the players and their trainers and the tour and everybody should try their very best to try to make sure they can avoid injuries. Is that by playing less? Is that by training different? Is that by playing a different schedule?

“Whose responsibility is it at the end of the day? I think it’s the players’. Sometimes you do get unlucky. Like a soccer team, sometimes you have seasons where more guys are hurt than others.

“I think we’re professional, we know how to warm up, we know what to do. Later on things become a bit more tricky. But I think that goes with the business.”

Federer heads into the Australian Open favourite to win the title (Getty)

Federer, who plays his first match against Aljaz Bedene on Tuesday, did not go along with a suggestion that he had retained his fitness because he is an attacking player who likes to shorten the points, while players like Nadal, Djokovic and Murray are baseline grinders.

“The off-season is tougher than playing tournaments – for me anyway,” he said. “I work hard in the off-season to create a base that serves me well throughout the season and then I rework the base time and time again throughout the season. I think that’s very important.

“I think attacking tennis also has a lot of wear and tear on the body, because being highly explosive is something that’s a big challenge. Playing more of a reactive game is maybe more physical in the sense that you play longer rallies, you spend more time on the court, but it’s always pretty much the same. It’s a similar rhythm. There aren’t that many sprints going on.

Andy Murray will miss the tournament after hip surgery (Getty)

“We talk about Murray and Djokovic being grinders. but I think they actually play quite aggressive. Everybody does. Even Rafa is standing closer to the baseline than he ever has in the past.

“Injuries can occur in one single moment, like when you come down from a serve. You’re like: ‘How did that happen?’ Sometimes you just don’t know. Sometimes it’s unexplainable how certain injuries happen.

“I’ve played thousands of matches in my life and I’m sure I’ve gotten lucky throughout my career. But sometimes you have to take a minute and talk to the team about it, like how we’re going to approach these next three months, next year, next day. Everything needs to be perfectly planned, I think, to avoid as many injuries as possible.”

Novak Djokovic has only just confirmed his fitness for the Australian Open (Getty)

Federer’s expectations here this year are very different to 2017, when he played his first competitive tournament for six months but went on to take the title after winning three of his matches in five sets.

“This year I hope to win the first few rounds and get rolling hopefully, whereas last year I was just hoping to win,” Federer said. “It was more of a ‘Let’s see what happens’ kind of tournament, maybe similar to what Novak or Stan or others are going through this year.

I play down my chances just because I don’t think a 36-year-old should be a favourite. That should not be the case Roger Federer

“It was a case of: ‘Let’s just see what happens, I’m not at 100 per cent, but you never know in a week’s time what’s going to be happening. If you’re in the draw, you give yourself a chance.’ That’s what happened for me last year. It all ended up way better than I thought it would.

“It was the tournament of the year for me, no doubt about it, with all the five-setters as well. Having no expectations was so nice after all these years always having expectations, which I have this year again.

Rafa Nadal has not played any competitive tennis in the lead up to the Australian Open (Getty)

“With age, I feel like I play down my chances just because I don’t think a 36-year-old should be a favourite of a tournament. That should not be the case. That’s why I see things more relaxed at a later stage of my career.”

Federer is the firm favourite to win the title but insisted: “I feel like maybe somebody like a Rafa, with the year that he’s had, and Novak with the six titles he’s had here, even if it’s unknown how he’s feeling, they could very well be the favourites too. At the end of the day, it’s all just talk beforehand.”

Stan Wawrinka is another who is struggling for fitness (Getty)

Federer said he felt in good shape and had had perfect preparation for the tournament both at the Hopman Cup in the first week of the year and in practice here for the last few days.