Michelin advised Edwards against tyre

The American preferred to follow his own choice and ran with the leaders initially, but lost grip later in the race and tumbled down the order.

"With Valentino (Rossi) we were very confident, but Colin chose a different family of tyre to those chosen by Valentino so it's not so easy to do a straight comparison," Yamaha's Michelin engineer Pierre Alves said.

"He really didn't like the tyre that Valentino chose. He couldn't get on with it."

Edwards admitted that he was struggling to get Yamaha's package to suit him.

"I don't have much positive stuff to say about today's race," he said.

"I had hoped that I would be able to try for a podium but right from the start I didn't have any rear grip and it was all I could do to keep it upright throughout the race.

"I genuinely believe that our bike is the best on the grid and I've never felt happier with it, but unfortunately the package as a whole isn't working for me at the moment and we need to understand why.

"I had a slightly different tyre to Valentino but he really showed his class again today. I just want to forget about this race and look forward to Le Mans, where I've always gone well."

Team boss Davide Brivio denied that Edwards' difficulties were harming Rossi's title challenge.

"Is it just a matter of taking points away from our rivals?" he said in an interview with Italia1 television.

"Who wins a championship does it mostly on his own. Valentino did that in 2004 and 2005.

"As for taking points away from the rivals it's a nice idea, but it isn't always do-able.

"Today Colin chose to use a different tyre and set-up, and had some problems."