Valentino Rossi cautiously upbeat about Ducati's new bike

The team tried a revised version of the GP12 with a part aluminium frame over the past two days at Valencia. While Rossi feels the chassis remains a work in progress, he was upbeat about the larger engine after ending today's session sixth quickest.

"These were two important days of testing because we needed to collect a lot of data for the next few months of work, which will be crucial," he said.

"The positives of this bike are certainly the engine, which I like, and the fact that it handles a bit better than the previous one. It's definitely more fun, in part because you can get sideways more.

"The frame isn't bad, but it needs work. We have to improve the braking, because I need to brake harder and later, and we need to improve traction under acceleration. Filippo [Preziosi] has many ideas, and now we have a little time to apply them before next year's tests."

Test rider Franco Battaini was called in to join Rossi for the Valencia runs as Nicky Hayden had to pull out due to a wrist injury sustained in Sunday's startline crash in the track's grand prix.