Tim Henman believes Novak Djokovic can remain at the top for years, but Rafael Nadal's intensity may see him quit earlier.
With Roger Federer now 39-years-old and past his best, Nadal and Djokovic are the top two players on the ATP Tour and have developed the most elite rivalry in modern tennis.
Henman, though, believes it may just be a matter of time before Djokovic is the last of the big three left standing, because physically he has a lot more left in the tank than his rivals.
“Certainly in Novak’s case, he has many more years," Henman told the Radio Times.
“Physically he’s in such good shape and I think his game doesn’t take so much out of his body.
“He looks like he’s less susceptible to injuries whereas Rafa’s game does take so much out of him mentally and physically, and you have to wonder how long he will keep going for.
"But I certainly see Djokovic at the top of the game for a few more years yet.
“You look at their consistency and you look at the top three having won 57 Slams, it’s just absolutely incredible and it doesn’t seem as though it’s going to end any time soon."
For more exclusive content from Tennisbuzz, including news, features, trivia, promotions and more, please be sure to sign up for our newsletter below or via our home page.
Why not test your tennis knowledge by tackling one of our fiendish quizzes too?