Osaka silent over ex-coach lawsuit as Miami Open begins

Christopher Jean, who helped Naomi Osaka when she was a junior, wants at least $2 million of her $10 million earnings to date.

Naomi Osaka says she is still learning about the difficulty of dealing with the trappings of fame and becoming the world's top player.

World number one Naomi Osaka refused to become embroiled in a dispute with one of her former coaches who is suing her for 20 percent of her career earnings.

Christopher Jean, who helped the Japanese two-time Grand Slam champion when she was a junior, wants at least $2 million of the $10 million of her earnings to date.

Jean insists Osaka's father, Leonard Francois, had signed a contract when he was coaching the 21-year-old and her sister Mari in 2011.

Osaka told AFP she was “not allowed to say anything” about reports of the lawsuit, although sources close to the Japanese star stressed they are not fearful of the outcome and believe the matter will be resolved shortly.

When asked about the difficulty of dealing with the trappings of fame and becoming the world's top player, however, Osaka admitted she is still learning.

“I am still relatively new at this so I can't really say yet,” she said. “But maybe as more time goes on I will be able to get a better grasp of the situation.”

Osaka spoke as tournament play began at the Miami Open, being staged at Hard Rock Stadium for the first time after decades at Key Biscayne.