Miami – World number one Naomi Osaka refused on Wednesday to become embroiled in a dispute with one of her former coaches who is suing her for 20 percent of her career earnings.
Christophe 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," she added.
TMZ, which reported the lawsuit, says Osaka attorney Alex Spiro calls Jean's claim "absurd" and adds: "This case has no merit and we will move past it."
Osaka spoke as tournament play began at the Miami Open, being staged at Hard Rock Stadium, home of the NFL's Miami Dolphins, for the first time after decades at Key Biscayne.
After losing in the round of 16 while defending her title at Indian Wells, Osaka hopes to regain the form that has seen her win the past two Grand Slam titles at this year's Australian Open and last year's US Open.
"Everyone knows that Indian Wells and Miami are like two slams so I feel there is a lot of motivation to win these tournaments," Osaka said.
"Beating Serena Williams in Miami last year was such a good memory — the first time I had played her — and I came straight off winning Indian Wells. I just wanted to test myself against her and from then on it felt like a dream.
"To win here would mean so much. I grew up watching so many great players winning here and was actually in the stands for one of the finals. Just to come from being a kid in the audience to be the person holding the trophy would be special."
There have been 13 different winners in 13 WTA events so far this year, with Canadian teen Bianca Andreescu the first wildcard to win at Indian Wells.
Osaka, whose sister Mari was due to face American Whitney Osuigwe in the first round, is on her guard.
"Everyone is really motivated by whoever wins the week previous and you can see that," she said.
"Everyone is at the same level so it comes down to who wants it the most and is willing to put in the work," she added.
The $72 million spent on turning a former Super Bowl stadium into a tennis venue has received good reviews from players.
A 5,191-seat main court — where former world number one Victoria Azarenka defeated Dominika Cibulkova 6-2, 3-6, 6-4 — has been created while two further show courts and eight other courts have been built on top of parking lots.
"I've never imagined ever playing tennis at Dolphin Stadium," Osaka said.
"We actually drove past it a lot when I was a kid. There's a lot space here, which is good," he added.