Vinales, joining the Japanese squad to replace three-time champion Jorge Lorenzo, has topped the tests he has taken part in with his team at Valencia last year and at Sepang this week.

The Yamaha rider admitted he has been surprised by how quickly he has adapted to his new bike, and Honda rival Marquez reckons he looks faster than Rossi over a single lap.

The three-time champion is convinced Vinales will be a threat in the championship battle this year, although he is aware that Rossi will be in the fight as well.

"I think [Vinales] is ready to fight for the championship. And to win it," Marquez told Gazzetta dello Sport. "So are Valentino and [Dani] Pedrosa.

"Lorenzo is struggling but he's on his first days [with Ducati]. I think the Yamahas will be the hardest to beat in the fight for the title.

"Maverick is riding very fast and feels very comfortable with the Yamaha, but when the championship starts it's all different.

"I don't know if he will be a bigger threat [than Rossi], because Valentino has more experience, and he's hungry. He's in front every Sunday.

"In any case, in terms of speed I see Maverick as the stronger rider."

Marquez says he is not sure the rivalry between the two Yamaha teammates will actually help him, as he reckons it might just make his opponents be even more competitive.

"Do I want them to fight between them? Yes and no, because often you try to beat your teammate and you ride even faster than before. At the end of the day he's your first rival," Marquez added.

The Spanish rider reckons Lorenzo, now with Ducati after leaving Yamaha, could be fighting for victory at the start of the season, but Marquez is not convinced his compatriot will be able to sustain a year-long challenge with the Italian bike.

"He will be competitive in many races. He might win in Qatar, a circuit when both Jorge and the Ducati go very quick. But for the championship I think the Yamahas are a bigger threat."