'He's always working on different things' says Kokkinakis talking about reasons for Federer's longevity

Thanasi Kokkinakis has revealed that Roger Federer's desire to continually improve his game and try shots that other players will not is the reason for the Swiss ace's ability to remain at the top of the sport for as long as he has.

The 21-year-old Australian, who has played just one tournament since the end of 2015 due to injury, is making a comeback tour in 2017. He practised with Federer in Dubai recently and admitted that he learned a lot from the 18-time men's singles Grand Slam champion on the fitness front and in terms of improving his game.

Federer has surprised everyone including himself with his form in 2017. The 35-year-old, who missed six months of last season with a knee injury, has made a better than expected start and gone on to win three — the Australian Open, the Indian Wells and Miami Masters — of the four tournaments he has played and is currently on a 19-1 win-loss run.

Federer has risen from world number 17 to world number four in just three months. He decided to take an eight-week break after the Miami Masters. That will see him miss the four clay court tournaments leading up to the French Open, which will be his only appearance on the red surface this season. The Swiss star is keen to remain fresh and peak at the major tournaments mainly Wimbledon and the US Open.

"I was trying to get as much information as I could from him," Kokkinakis said after training with Federer in Dubai, as quoted by Tennis World USA. "I'm only 21 now, and he's 35 but I feel like I've still got to kind of manage my body the way that he does to be honest, because I can't put too much load on it, because I don't know what my body can take at the moment."

"What sticks out for me is that he's always working on his game, he's always working on different things where he can improve. Trying shots where maybe a standard tennis player wouldn't really consider as a possibility and I think that's what has put him that level above for so long and that's what's kept him able to play for so long."