Seven-time Grand Slam champion Justine Henin says Naomi Osaka is a complete player and the leader in women's tennis right now.
Osaka already has four Slam titles to her name aged 23 and Henin believes the influential Japanese player could dominate the women's game for years to come.
"I'm really much more positive than I was two years ago because I feel that we have some stability in women's tennis," Henin told Sky Sports.
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"I think with Osaka we have someone who can really lead the women's game in the next few years.
"When she won her first US Open and Australian Open everything seemed new for her and she took a while to assume her status because when she became number one it was really tough for her. She was really shy and it was complicated.
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"As a player I thought she was impressive already but she has improved physically, she's moving really, really fast and she's much better on the court now. The speed and velocity of the forehand is quite amazing. She can do a bit of everything.
"She has great vision and she has improved mentally. At the Australian Open she saved two match points against Garbine Muguruza.
"Her serve reminds me a bit of Serena Williams who sometimes wasn't playing so well but times when she had to play well she was doing it.
Naomi is charismatic and a complete player. She plays fast, she's consistent, and she has physically improved a lot, so I'm very impressed by the level of the game she can reach.
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Henin believes the level of competition has improved greatly at the top of the women's game and Serena Williams, 39, could find it tricky to lift a record-equalling 24th Grand Slam title at Roland Garros.
She added: "I think it's going to be really, really hard also because she is a mum now and emotionally she has changed. She still has that fire in her belly, but is it the same as it was before when there was only tennis in her life? That's also a bit of a question.
"I think she wants to be there. She still has the passion but now she's a mum, she has different things to deal with and that changes life. At nearly 40 to still be there, I admire her a lot, but it's going to be tough."
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