Checa: I still don't understand.

Fortuna Yamaha's Carlos Checa suffered a mysterious high-speed fall in the closing stages of today's final qualifying session at Phillip Island, which contributed to him being left 13th on tomorrow's grid.

The accident marked a day to forget for Checa, who this morning was confirmed as being replaced by Colin Edwards at the factory Yamaha team from next season.

"That was a big crash and I still don't understand it," said Carlos afterwards. "I went out for a fast lap and had let some riders get ahead on the previous lap in order to get some clear track. When I went into turn six both tyres just went. My feeling was that it was the front, but it felt a bit strange.

"With a race tyre the bike is quite good here," he added. "We had a good pace, and I was confident I could improve my lap from before but it was not the case."

Checa's team-mate Valentino Rossi will start second.