Hayden mystified as to cause of fall

The American former world champion was fifth fastest and out-pacing his team-mate Casey Stoner when the accident happened in the final quarter of the session, and Hayden admitted afterwards that the sudden loss of grip took him completely by surprise.

"We started out well and on my first exit on a hard tyre I was able to improve my lap time quite a lot," he said. "We got into the 1m57s quite quickly and I thought we were in good shape to have a shot at a good grid position.

"Unfortunately my first flying lap on the softer tyre ended in turn three - I just lost the front quite early on entry, I don't know why. I know people always say 'I did nothing different!' but honestly, even looking at the data, the brake pressure and speed was the same as my previous runs.

"We need to have a look at that and understand it tonight."

Hayden's hand was damaged when it got trapped between the asphalt and the left handlebar. The injury caused him difficulty when he returned to the track on his spare bike at the end of the session, but he said he expected to be able to race with it.

"Luckily it wasn't too heavy and everything on my body is fine other than my left hand," he said. "It must have got caught under the bike because it's very sore and even though we tried to go back out I couldn't change direction.

"We've had it checked out by x-ray which showed we chunk off the tip of the radius, which isn't good, but my scaphoid is okay and that's the main thing because I have a screw in there and it's not damaged.

"Just walking around the paddock it's not too painful but we'll have to wait and see how it goes over 22 laps on the bike tomorrow."