Melbourne: Japan`s Kei Nishikori won high praise from Rafael Nadal Monday as the world number one tipped him to break into the top 10 following their hard-fought encounter at the Australian Open.

The Japanese star, advised by Michael Chang, kept the 13-time Grand Slam champion on court for three hours 17 minutes before going down 7-6 (7/3), 7-5, 7-6 (7/3) in the fourth round.

Asia`s most accomplished men`s star said he was proud of his efforts, but also disappointed to lose his sixth straight match to the mighty Spaniard and fail to take a set.

"First of all I`m really disappointed because I had some chances to at least get one set, and I couldn`t," he said.

"I mean, both tiebreaks he was playing much better. He raised his level and he was playing good.

"But a couple points was amazing points. I thought I was playing good. Some important points I couldn`t get and the games can change completely.

"So, you know, I think that was the best game I have against Rafa."

Nadal said Nishikori had come a long way in a short time and had a bright future.

"It`s always it`s tough against him on every surface," said the Spaniard.

"He`s a very complete player. He`s very quick, he`s able to do the most difficult thing in tennis, that`s taking the ball early and changing the direction. He`s able to do it easy.

"Kei is a potential top 10 player."

Nadal added: "It was difficult for me to take positions inside the court and I was close to losing every set, so I congratulate Kei and I feel he will have a great season."

Nishikori, who is currently ranked 17, has hired former French Open champion Chang to help him crack the top 10, working alongside his current full-time coach Dante Bottini.