"I think he can play as long as he wants to on the mental side. Physically, I think he can play for another four-five years without any problem," said Roche.
Asked about Federer adding another major to his record 17 titles, Roche said, "Another Slam definitely... Obviously, Wimbledon is his best chance but he's knocking on the door in last few Slams. As long as the guys still respect Roger, he is always going to be a threat," the Aussie told reporters on the sidelines of a seven-day camp at the Jaidip Mukerjea Tennis Academy here.
With fluent skill that comes so natural to him, the biggest advantage for the Swiss great is to stay injury free, Roche said.
Revealing his former ward's secret to stay injury free, he said: "It's the way he hits the tennis ball so fluently it's not so physical as a lot of the other guys...
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The former French Open winner also coached Ivan Lendl and he said the Czech's success was through sheer hard work.
"Lendl on the other hand achieved greatness through sheer hard work. He was not a great talent but realised that for him to win Slams and dominate he had to change his ways which he did."
With the Indians struggling to keep pace with the modern day's power packed tennis, Roche cited the example of Kei Nishikori who finished runner-up in the 2014 US Open and became the first Japanese to break into top 10.