Stoner could miss pre-season testing in Sepang on 22 January

But he will need to rest for up to eight weeks to allow it to heal.

The 22-year-old may now miss the first pre-season test dates of 2008 while his fitness training during the winter break will be restricted.

The Ducati rider was forced to miss his team's MotoGP title celebrations in Bologna, Italy last weekend.

"It's never fun [getting injured] but I'd rather it happened when you have a couple of months to recover," he said.

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Stoner is being assessed by the same medical advisors who successfully operated on his right shoulder at the beginning of last year.

He secured his first MotoGP world title at the Japanese Grand Prix in September, with three races remaining, becoming the second-youngest winner.