Japanese tennis player Naomi Osaka has announced she will no longer be working with Jermaine Jenkins, who had been coaching her since February.

“I’m super grateful for the time we spent together and the things I learned on and off the court but I feel like now is (an) appropriate time for a change,” said Osaka in a message on her Twitter account.

“Thank you for everything, it was a blast,” she added.

Osaka, 21, hired Jenkins after she parted ways with coach Sascha Bajin within weeks of winning her second consecutive grand slam at the Australian Open, and becoming world’s top ranked female player.

She has not made a final since then and dropped down the rankings to No 4.

At the French Open she was knocked out in the third round, followed by a first round exit at Wimbledon.

Osaka’s defence of her US Open title ended with a fourth-round loss to Belinda Bencic.