Biaggi: Stoner is at Rossi's level

Rossi has dominated the sport for several years, and while Nicky Hayden won the title for Honda in 2006, Biaggi believes that only Stoner is at the same level as the Yamaha rider.

"Casey is the guy who is going to push hard and make trouble for Valentino," Biaggi told autosport.com. "At the end of the day it is going to be these two.

"People say that it has been all because of the Ducati, but I think Casey is making the difference. Look at what (Loris) Capirossi has done for most of this year."

The four-time 250cc world champion added that he believes having Stoner as a challenger to Rossi will benefit the sport.

"I think there is Rossi, and now there is Casey as well, so it should make it much more interesting," he said.

"Casey has already beaten Valentino many times, and it will be tough until the end of the season, if he doesn't win the championship before the end."