Having lost out to MotoGP World Championship leader Valentino Rossi during a thrilling Laguna Seca duel just before the summer break, the last thing Casey Stoner needed - for the championship or his confidence - was another defeat, let alone his first non-finish as a Ducati rider.

But that's exactly what happened at Brno on Sunday, with the reigning title holder - who came into the event stating his intention to go the full race distance with Rossi and put pressure on the Italian in the closing laps - falling from the lead on lap seven of 22, just as Rossi had begun to reduce the Desmosedici rider's 1.2sec advantage.

"Obviously we are all disappointed with this result because our pace in practice was good, everything went very well [in warm-up] and we felt we could push out in front," admitted Casey, who had taken his sixth consecutive pole on Saturday.

It looked to the watching world like Stoner had fallen as he attempting to respond to Rossi's increasing pace. The Australian said he was unsure what exactly had happened, but accepted full responsibility.

"Things were going according to plan until the crash. I was doing the same lap time over and over and I was quite happy with the pace I was running," he said. "The crash came out of the blue, that corner was an easy one but I lost the front and it happened very quickly, very suddenly and I didn't manage to save it. It's a hard one to explain and we will look at the data but sometimes this kind of crash happens at this level of racing and it was my mistake."

Stoner has now fallen in the last two rounds while battling Rossi, but Sunday marked the first time the reigning world champion has not made it to the chequered flag since signing for Ducati at the start of 2007.

Most significantly in terms of the championship, it means that all Stoner's hard work in closing down Rossi's advantage with successive victories at Donington, Assen and Sachsenring - prior to Laguna Seca - has been undone.

Stoner is now 50 points behind the Italian rider, back where he'd been after the Catalan Grand Prix on June 8, and - with just six races remaining - is opening doubting his title chances.

"We knew that we needed to win this race - and more - in order to close down Valentino's advantage so this makes the championship very difficult for us," said Stoner. "Anything can happen in racing but 50 points is a big gap against such a strong and consistent competitor.

"Anyway I never throw in the towel, nor does anybody at Ducati, and we will keep fighting until the end," he insisted. "Misano is a home race for the factory and there will be lots of Ducatisti there, so my main thought now is to stay positive and bounce back with a good show for them in two weeks' time".

"I'm obviously disappointed for Casey because after another incredible weekend it's a small mistake - his first in a race since he's been riding for us - has cost us very dearly," commented Ducati MotoGP project director Livio Suppo. "Anyway, we have to think positive and continue to work hard to put him in the right conditions to ride as hard as that in the six races that are left."

To see full picture coverage of Stoner's fall CLICK HERE