After second (wet) and fifth (dry) with the new Ducati GP11.1 in free practice at Assen, Valentino Rossi suddenly dropped down the timesheets to eleventh in Friday afternoon's qualifying session.

The Italian superstar explained that he struggled to generate heat in the rear tyre - but still backed the decision to switch bikes for this weekend's seventh round.

"We're disappointed with qualifying because we had started quite well yesterday, so clearly, we expected things to go better today," said Rossi. "We had a decent session this morning, but we weren't able to improve, so we'll start eleventh.

"The rear of the GP11.1 is better than the previous version, but we weren't able to find a setup that allowed us to bring the tyres up to temperature, and at the moment, that's making it difficult to find the feeling I need to ride hard and be strong on corner entry.

"I don't think we've yet learned how to properly adjust the bike, and that's something we knew could happen since we have so little time available. Still, this all helps us to gather experience for the future, and we have some ideas for tomorrow's warm-up session that we hope will help us go faster in the race."

Rossi, like team-mate Nicky Hayden, has taken just one podium with the standard GP11 - and many believe Ducati are using Assen as a kind of test session ahead of their all-important home Italian round, at Mugello next weekend.

Hayden, still using the GP11 albeit with a new 'softer' chassis design, qualified in ninth place, on a day when rookie Karel Abraham was the leading Ducati rider, in seventh.

Hayden felt qualifying should have been stopped when Loris Capirossi fell in the closing ten minutes.

"This morning we were trying to learn the step 2 chassis, but with the rain, we never got to compare back-to-back with the step 1 in similar conditions so, for this afternoon, we went with what we knew," began Hayden.

"We struggled a bit at the beginning of qualifying, and then when we put in the soft tyres, we also changed to a different shock setting that helped put some temperature in the tyre. I started getting a better feel and going faster, and like always, it would have been nice to get a few more laps.

"It's not why we're on the third row, but when Capirossi crashed, they should have red-flagged the session, because he was in the run-off area of a fast place. We've had just about every condition this weekend, so we'll see what we get tomorrow. It could be a wild race."