On paper, 2007 MotoGP world champion Casey Stoner had a good opening day of testing at Sepang on Thursday - setting the second fastest lap time - but the reality was somewhat more worrying.

The Ducati Marlboro star is making his comeback after three months out of action due to wrist surgery, but the Australian was left 'in a lot of pain' on Thursday and unable to more than a handful of consecutive laps.

"This morning was really difficult, I really didn't feel comfortable on the bike," said Casey. "My wrist is still in a lot of pain and I honestly hoped it would be in better shape than this after three months since the operation. Even though the lap times were good from the start the wrist was still giving me a lot of problems - it is weak and painful under braking, especially in the first left-hand turn.

"I can't do more than four or five laps at a time and there's nothing I can do about that at the moment, other than hope that it improves over time. Sepang is a physically demanding circuit and probably not the best place to be riding for the first time after three months out. I preferred not to ride too much and tire myself out and hopefully it will already be a bit better tomorrow. Freddy, our physiotherapist, has a bit of work to do tonight!"

Nevertheless, Stoner was on the pace throughout the day as he evaluated the latest developments for the Desmosedici GP9.

"The GP9 is running well and I have the same positive feeling as the last two tests at Barcelona and Valencia," said the #27, who lapped less than two tenths behind fastest man Loris Capirossi. "The chassis is completely different and we'll have to work on improving the set-up but we have a good starting point and we can use the GP8 as a reference.

"The power delivery has improved and now we have more torque, which helps on the exit of the slower corners. Bridgestone have brought two compounds here that both work well, although I prefer the harder one because even though it is a little more difficult to ride it guarantees a more consistent performance."

New team-mate Nicky Hayden was eleventh fastest.