Japan's [Images] number one Kei Nishikori has been warned not to let his mobile phone go off on court during next week's home Davis Cup clash with China.

The 19-year-old has been told to leave his phone in the locker room after it kept bleeping during a first-round defeat in Memphis last week, Japanese media reported on Wednesday.

"He will have to be very careful about his mobile phone," said Japan's Davis Cup coach Eiji Takeuchi. "I'll be warning him about that just to be on the safe side."

Nishikori had left his phone in his jacket pocket while playing Cypriot Marcos Baghdatis [Images] and ended up a 7-5, 6-3 loser, later admitting the incoming call had put him off.

"At the very least he will have to learn to put it on vibration mode," added Takeuchi, who also selected Go Soeda, Satoshi Iwabuchi and Takao Suzuki for the tie with China.

Nishikori's popularity has surged in Japan since he became his country's first winner on the men's ATP Tour at Delray Beach in February last year.

The Florida-based Nishikori has slipped from a career-high 56th in the world after his breakthrough victory to his current ranking of 93.

Japan are aiming to make the playoffs for the chance to return to the Davis Cup World Group for the first time since 1985.

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