Defending Mugello winner Casey Stoner had a nightmare start to the 2010 Italian Grand Prix, when he fell from his factory Ducati in the opening minutes.

The accident was his fourth in as many events, but this time it was a braking problem than triggered the tumble, rather than a repeat of his previous front-end troubles.

"I think I only managed three 'proper' laps and none of them were decent!" said Stoner at the end of the session, in which he was only seventh fastest, almost 1.4sec behind Valentino Rossi.

"I had a crash at the start, which obviously didn't help. Basically when I went to grab the brakes at the "Bucine" corner there was nothing there! I tried to tip the bike into the corner but she was skipping wide so I just had to run her into the gravel."

After running off track, Stoner's Desmosedici washed out from under him in the loose gravel. "Stones got everywhere and that kind of stuffed that bike up for the rest of the session," said the Australian.

Stoner was aiming to use the hour to do extensive back-to-back testing of the 2009 and 2010 Ohlins front forks, in an attempt to cure his front-end falls.

The crash made that difficult, but the 2007 world champion felt happier on last year's equipment and has now switched both his bikes to the older design for Saturday.

"It was a shame because we'd switched back to the old forks on that bike and even though I only had a couple of laps on them it was enough to make me want to use them on both bikes tomorrow," Stoner confirmed.

"The feel with them is more aggressive but we have feel," he explained. "The other bike had the new forks on but I just don't have the same confidence with them and I was losing the front in the same kind of corners that I have been in the last races.

"Nothing we tried seemed to work today, it was just one of those days! All we can do is start again tomorrow - hopefully the weather stays good because we need laps."

Team-mate Nicky Hayden made a slow start to the session, but climbed to ninth by the flag.

"Today wasn't as smooth out of the gate as we would have liked," said the American. "The bike didn't feel too bad but we were struggling in some of the downhill corners to get it to hold the line and change direction without using the brake to get the weight onto the front.

"We certainly need to take a good look at things together tonight and see where we can make it better because nothing came easy out there.

"It is not just a front-end thing, we need a little bit of improvement all over the bike. I know my guys will be working hard as always and tomorrow we need to get our head down again because this is such an important race for Ducati."