PERTH, Dec 30 — Japanese star Kei Nishikori pulled out of the inaugural ATP Cup today as he continues to struggle with an elbow injury that has kept him out since the US Open.

The former world number four, who has slipped to 13, said he was disappointed not to be representing his country in Perth at the team event starting on January 3.

"Today, together with my team, we have made this decision as I am still not 100 per cent ready to compete at the highest level,” he said in a statement.

Nishikori’s elbow needed surgery in October and it is unclear whether he will be fit for the Australian Open when the first Grand Slam of the year begins at Melbourne Park on January 20.

Yoshihito Nishioka will replace him as the top-ranked player in Japan’s ATP Cup team.

Yasutaka Uchiyama also withdrew from the event earlier this week, with Toshihide Matsui taking his place.

Nishikori’s absence is another blow for the event after Britain’s Andy Murray pulled out over the weekend with a pelvic injury and Roger Federer opted not to play.

The innovative team championship, from January 3-12, offers US$15 million (RM60 million) in prize money and a maximum of 750 singles and 250 doubles ATP rankings points.

It will see 24 nations split into six groups, with eight teams emerging from the round-robin stage to compete in the knockout phase.

Sydney will host the finals, along with group games which will also be held in Brisbane and Perth. — AFP