Japanese ace tennis player Kei Nishikori will sit out the remainder of the season as he has ruptured a tendon in his right wrist, his management firm said Wednesday.

Nishikori, ranked ninth in the world, withdrew Sunday from the ongoing Western and Southern Open, a tuneup to the U.S. Open starting late this month in New York, after experiencing pain in his right wrist during practice.

The 27-year-old heard a popping sound in his wrist when he served during the training session in Cincinnati and rushed to a hospital where he underwent an MRI examination and also had it seen by several other specialists, the firm said.

There are no plans for him to undergo surgery for the time being, according to the firm.

Nishikori has been suffering from problems with his right wrist on and off this year.

He played through nagging pain and aggravated it at the Miami Open in March where he was knocked out in the quarterfinals, while he forfeited his quarterfinal match against Novak Djokovic at the Madrid Open in May over the issue.

The best finish in the majors this year for the 2014 U.S. Open runner-up was making it to the last eight at the French Open in May-June. The last time he had a season without any tournament championships was in 2011.

Nishikori reached the top 10 in the men's world rankings in May 2014 and has remained there continuously since September that year, but is likely to drop out due to his absence.