Reigning MotoGP world champion Casey Stoner endured a tough comeback from injury on the opening practice day at Motegi, ending the two sessions in seventh position.

Stoner's Repsol Honda RC213V suffered a technical failure moments after leaving the pits for the start of FP1 - and he later lost further valuable track time due to a brake issue in FP2.

He eventually finished the day 0.890s behind team-mate Dani Pedrosa.

The Australian star, back in action for the first time since suffering ankle fractures and ligament damage in a qualifying spill at Indianapolis in August, was forced to adapt his riding style at Motegi to cope with the injury.

"Today was a little disappointing, this morning we had our first bike fail on us so we lost valuable time, then in the second session we had a brake issue and spent a lot of time in the garage fixing that also," said Stoner.

"We spent the two sessions trying to find a nice balance with the bike, of course I'm not feeling 100 per cent as it is, so I wanted to get a reasonable feeling with it before I start pushing.

"At the moment the acceleration points are causing me most difficulty as there are many areas at this circuit where the bike wants to wheelie and you need to keep your body and weight over the front of the bike," he added.

"Unfortunately my foot doesn't want to bend far enough to help me move forward so I'm having to pull myself forward which is giving me issues with my arms as they are working a lot harder than usual.

"We'll keep working tomorrow and see what we can do."

Stoner is third in the championship, with four wins this season, but is now just seven points ahead of Andrea Dovizioso after missing three rounds.