Chinese tennis great Li Na said US Open champion Naomi Osaka can go on and win multiple Grand Slam titles - if she can find the inner desire to match her physical abilities.

Osaka has admitted feeling burdened by expectations after last month's stunning victory in New York, saying she puts pressure on herself to "do more, do better".

The 20-year-old world No 6 was also in tears after her "bittersweet" US Open win, which was marred by Serena Williams' explosive argument with the chair umpire.

"I believe with her abilities and strength, she can win many Grand Slam titles - that is if she really has the desire to be a champion," Li said at the ongoing Hong Kong Open.

Osaka, Asia's second Grand Slam singles champion after Li, has pulled out of the tournament with a back injury.

Williams, 37, brought a halt to her season after the US Open final, where her latest attempt at a record-tying 24th major title ended in acrimony.

But Li, the former French Open and Australian Open winner who retired in 2014, cautioned that it was unwise to judge Williams, who returned to the circuit this year after becoming a mother last September.

"Looking at the players from the sidelines, we might not really understand some of their psychological goings-on on the court," said Li.

"I've always thought Serena is a very strong player. There are very few players who can give birth and then immediately come back.

"For me, it's really hard to find a balance between family and the tennis court, but she very quickly got into the US Open final."

Li is often credited with igniting tennis interest in Asia and especially in China, but she said the sport still had a long way to go.

"Tennis in Asia is still in its adolescence. We have just passed the infancy stage, so we can still go a lot further," she said.

Agence France - presse