Tennis is in a transition time now.
And when the dust settles from the growing generational clash, Rafael Nadal believes there's one man who could stand atop the world rankings: Nick Kyrgios.
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The 14-time Grand Slam champion endorsed both Kyrgios and his Australian Davis Cup teammate, Thanasi Kokkinakis as leaders of the ATP's young generation.
In an interview with the Herald Sun, Nadal calls Kyrgios' potential "unbelievable" and asserts the volatile Aussie who upset him at the 2014 Wimbledon can reach world No. 1.
"In this new generation you will need to see how Kokkinakis will evolve, he suffered an injury and we don't know how he will comeback," Nadal told the Herald Sun. "But he has the potential to be at the top.
"Kyrgios is already at the top. (He is) a player who has unbelievable potential. He has (to) focus on himself, and he can become world number one and win a Grand Slam."
Former US Open champion Andy Roddick told Tennis Now earlier this year if Kyrgios can mature and bring concentration and commitment to every point, he "could be one of the greats."
"Kyrgios it's gonna be between the ears," Roddick said. "And he admitted that much (at Wimbledon). His upside is amazing. If you could combine his talent and his game with someone who may be more disciplined mentally, then you'd have someone who could be one of the greats."
The 21-year-old Aussie edged 17-time Grand Slam champion Roger Federer, 6-7, 7-6, 7-6, at the 2015 Madrid. Kyrgios is winless in five meetings with world No. 1 Andy Murray, winning just one of 15 sets they've played.
Kyrgios has yet to face world No. 2 Novak Djokovic. Kyrgios has split four meetings with reigning US Open champion Stan Wawrinka, including a 7-6, 7-6 victory in Madrid last spring.
The ballistic-serving, basketball-loving Aussie says if he can get fitter, he can rise to the top spot.
"Well, I have beaten three of the four, and I haven't played Djokovic yet. I don't think it's an exaggeration (to eventually reach No. 1)," Kyrgios told the media in Rome in May. "I think I still need a lot of time. I need to do a lot of hard work, a lot more matches. I need to grow more and become stronger and more fitter.
"I don't think it's an exaggeration at all. I've beaten most of them, anyway."
Photo credit: Tennis Australia