Greek star Tsitsipas ready for the top

With wins over the big three of world tennis already under his belt in 2019, Greek star Stefanos Tsitsipas said Thursday he believed he had the ammunition to take the world number one ranking.

Tsitsipas became the youngest player to beat Rafael Nadal on clay and the youngest to record wins over Nadal, Roger Federer and Novak Djokovic during a stellar 2019 which saw him rise to world number five.

The 21-year-old heads into the inaugural ATP Cup ranked sixth, but said he was confident he could go all the way to the top.

"I mean, yeah, they are still there -- they are doing really well," Tsitsipas said about Nadal, Federer and Djokovic.

"For me, it's very challenging to go out there and compete against them.

"I feel like there's something extra to chase after when I play against them, plus I get to learn a lot when I play against them.

"I feel more of a complete player," he added.

"I kind of compare them to me to see what works for them and what should I work on more, and they're just ...