Nick Kyrgios owns the explosive game to end Australia's Grand Slam singles title drought—but he must get fitter and tougher to realize his major potential, says Hall of Famer Ken Rosewall.

Tennis Australia honored Rosewall with a ceremony commemorating the 50th anniversary of his Roland Garros championship.

Watch: Hewitt, Kyrgios Partner

The eight-time Grand Slam singles champion believes Kyrgios has the talent to win Grand Slams, but adds "in some ways, (Nick is) his own worst enemy.”

The 23rd-ranked Kyrgios opened the season claiming his fourth career title in Brisbane, but has been pained by an elbow injury that forced him out of Rotterdam, Delray Beach, Acapulco and Indian Wells.

Kyrgios, who has not played a singles match since losing to Ivo Karlovic in Houston last month, must commit to conditioning says Rosewall.

"With the leading (Australian) players, there's been a few obstacles," Rosewall told The Sydney Morning Herald. "Nick is one that has more potential than anybody. He does have a physical problem, which is not his fault, (but) certainly he needs to work a little bit harder on his physical fitness."

Kyrgios owns a 5-2 career record in five-set matches; he is 24-22 lifetime in deciding sets (third or fifth sets).

"He doesn't seem to play any long matches," Rosewall said of Kyrgios. "I'd like to see them working harder on their game ... it might bring better results."

Hall of Famer Rosewall asserts both 36-year-old Roger Federer and 31-year-old Rafael Nadal will continue to be favored to win Grand Slam titles in the coming two years.

"I’m like millions of others, I’m a Federer fan,” Rosewall said. "I’d like to see him win some Grand Slams and I think he’s quite capable of doing that.

"The question with the younger players, I think they’re near, they’re getting nearer, but it might be another year or so before you could say that someone else is favorite for a tournament.

"It seems like another year or so that you’re going to say that Nadal or Federer are favorites for a tournament."

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