Rossi surprised by Stoner's form

The Australian rider currently heads Rossi in the MotoGP standings after seven rounds, and Rossi believes that Stoner has improved as a rider compared to last season.

"At the beginning of the season I knew that Casey was very fast but in the past he made some mistakes," said Rossi.

"Now he is very fast without making any mistakes, and he has done a great job. The Ducati is also very fast and good to ride."

Rossi lost out in a straight fight with Stoner last time out at Barcelona, but the Italian is not too concerned about the championship situation just yet.

"It is a difficult battle, but we try to fight," he added. "We are only 14 points behind Casey, it is a long season and there will be hard battles."

Rossi also admitted that while Stoner and Ducati made such a strong start to the season, his Fiat Yamaha team have made some errors in the early races.

"We made some mistakes at the beginning with the tyres, but we have quite good points," he said.