Reigning world champion Sebastian Vettel has singled out two leading challengers to his F1 title, and mentioned two more rivals that could spring a surprise.
"Alonso for sure, and Hamilton is without question one of the best drivers," the German told Sport Bild during an interview.
But Vettel has also warned rivals and pundits against writing off 2006 Ferrari teammates Felipe Massa and Michael Schumacher.
"He (Massa) didn't have a good season but no one should underestimate him; it's not so long ago that he was really strong," said the 23-year-old, referring to Massa's title challenge of 2008.
And Vettel said the same logic also applies to Schumacher.
"I think neither of them have forgotten how to drive," he said. "Schumacher's history is too great to write him off, and Nico Rosberg has also showed us his strength," he added.
Vettel also said Jenson Button has unique skills that kept him in last year's title race, and admitted that his own Red Bull teammate Mark Webber is similarly a threat.
"If our car is good enough, he (Webber) will get involved again."
On Webber, Vettel said he and the Australian have cleared the air since their 2010 clashes, but admitted that the pair are "not necessarily on the same wavelength".