Singapore - Li Na's Grand Slam future is "up in the air" after an injury-hit season and the loss of her inspirational coach, tennis great Martina Navratilova said on Friday.
The 18-time Grand Slam champion said Li's ability to withstand injuries was the critical question as she approaches her 33rd birthday in February.
China's Li won the Australian Open in January but her season has nose-dived and along with splitting with coach Carlos Rodriguez, she has also been sidelined by a knee injury.
"The body is the biggest issue for her, clearly, now," Navratilova said in an interview, when asked whether Li was capable of winning a third Grand Slam title.
"She had some motivation issues a year ago after Wimbledon but then she had a good talk with Carlos and then wins the Australian Open the following year.
"So she's had a great year, she won a Slam which is amazing. But now she may not play the rest of the year, so it's up in the air for her.
"Game-wise, does she have a Slam? Yes, but is the body going to cooperate?"
Navratilova was speaking during a promotional visit ahead of her WTA Legends appearance in Singapore in October, which will run alongside the season-ending WTA Championships.
Her comments underline the questions facing Li, who will miss the US Open and may not return until the inaugural Wuhan Open in her home city next month.
Li, ranked third in the world, has had dips in her career before but Rodriguez, the former coach of Justine Henin, was key to her most recent revival.
Navratilova, who won the last of her Grand Slam singles titles at 33, knows only too well the physical challenges that are facing the Chinese star.
"It's a tricky thing. When you get older you need to curb your schedule and not play as much," she said.
"But when you play too little then you're not match-tough, and then you start losing early and then you need to play more tournaments to get the matches.
"And then it really upsets your rhythm of getting ready, so it's tricky when you get older. You have to keep adapting."
Of Rodriguez's decision to stop coaching Li, Navratilova said "sometimes the relationship kind of runs its course".
But she said she was open to taking up a coaching role with a top player, following the example of Stefan Edberg, Ivan Lendl, Boris Becker and Amelie Mauresmo.
"I'd like to pass on the knowledge. There's no substitute for that one-on-one, getting into the nitty-gritty of the game," she said.
"And you can only really do that with a top player, when you're just searching for that little edge. That sliced backhand or the dropped volley that you may only use once or twice a match but may mean the difference between winning or losing.
"I love getting into those details of the sport. I'm sure it'll happen."