Rossi: Ducati to win more

The 28-year-old Italian finished second in the season-opening Qatar Grand Prix, behind first-time winner Casey Stoner.

But the five-time world champion's Yamaha was no match for the Italian machine down the straights due to what he believes is a relative lack of horsepower.

"We need to have some more power," he told Italian newspaper Gazzetta Dello Sport. "Our Yamaha will never go as quick on a straight as the Ducati.

"We have the feeling, the speed in turns. But we need to make the gap smaller to fight with Stoner.

"I don't think we can fix the problem in time for Jerez. It will happen later, I don't know when. We have new parts which we want to try straight away but we have no testing.

"In these conditions it is hard to compete, but in the turns we are faster than the Ducati: in some sections I was gaining a lot."

One positive for Rossi, who trails Stoner by five points in the world championship, is that the Jerez circuit lacks the long straights of Losail in Qatar, and his Yamaha is the best handling bike on the Moto GP grid.