Casey Stoner could be forced to miss some of the remaining MotoGP rounds after it was revealed his scaphoid injury could warrant an earlier than planned operation.

Stoner has been carrying the injury since 2003, but aggravated it with falls in Brno and Misano to the point that he admitted he was struggling with the ailment during the most recent round at Indianapolis.

Currently, the reigning champion is most likely to undergo surgery at the end of the season, which could well keep him off duty during at least some of the 2009 pre-season tests.

Indeed, Stoner admits he is not '100 per cent' at the moment and is reviewing his condition with every weekend that comes, starting with the next round in Motegi, Japan.

"I'm not 100% but I've got a few weeks to try and improve a few things," he told the official MotoGP website. "I do need an operation, but we'll race for as long as we can and try and do it at the end of the season. I don't think that we will do the tests at the end of this year; maybe Valencia but I'm not sure."

However, Ducati team manager Livio Suppo is not ruling out the possibility of withdrawing him from some of the remaining races this season if he finds he cannot compete with it.

"Let?s say that at the moment, it [the injury] is a problem in the races for Casey. He doesn't speak too much about it, but we will be taking things race-by-race. If the pain is manageable then he will finish the season, otherwise we will try and get something arranged earlier.

"At the moment it seems that he will be able to complete the year, but if he is operated on after Valencia then he will definitely miss the Jerez test - that's not a big issue as he doesn't need a lot of tests in which to understand the bike."