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The two-time grand slam champion withdrew from the season-ending tournament in Shenzhen on because of an issue with her right shoulder.

Osaka revealed she was troubled by the injury during her China Open triumph this month but hopes rest and rehabilitation in the off season will get her back to full fitness.

"I didn't serve for a while when I was in Japan," Osaka, who was replaced by Kiki Bertens at the showpiece in China, said.

"I just started serving [in] the last two days. Felt better, came here, then I played my match [a victory over Petra Kvitova on Sunday]. I felt it immediately. When I woke up the day after, it was throbbing and stuff. Yeah, I didn't serve at all [on Monday]."

The former world No.1 added: "I injured my shoulder like five years ago or something, but not badly. It was in Thailand when I was like 17 or something. It wasn't that big of a deal. I just had to rest it. I'm hoping it's more like that.

"It doesn't feel like it's anything more serious than muscular. I think if it was like bone-related then I wouldn't be able to lift it, but I am able to do that. It's just a little bit painful.

"Definitely I don't think it's something that I would immediately need surgery for. I've never had surgery, so I feel like I'm very lucky on that. I'm not really hoping that will change any time soon."