Vettel lists title rivalsposted in F124 | 02 | 2011

FORMULA ONE world champ Sebastian Vettel has named the two drivers he believes will provide the biggest challenge to him retaining his title; and the German has highlighted another two drivers who could well spring a surprise.

"Alonso for sure, and Hamilton is without question one of the best drivers," 23-year-old Vettel said, but he also warned rivals and pundits not to write off 2006 Ferrari team-mates Felipe Massa and Michael Schumacher.

"Massa didn't have a good season last year but no one should underestimate him; it's not so long ago that he was really strong," Vettel continued, referring to the Brazilian's 2008 title challenge. And he applies the same logic to Schumacher.

"I think neither of them have forgotten how to drive," Vettel, said. "Schumacher's history is too great to write him off, and Nico Rosberg has also showed us his strength."

And Vettel cast the net even further when he threw McLaren's Jenson Button, and his own Red Bull team-mate, Mark Webber, into the equation.

"Jenson managed to keep in the title fight right to the end of last season and if our car is good enough, he (Webber) will get involved again," Vettel, who said he and the Australian have cleared the air since their 2010 clashes, but admitted the pair are 'not necessarily on the same wavelength'.

"It's going to be another long, hard season."

Keep up-to-date with all the latest news by following us on twitter.com/scotcars

Jim McGill

PHOTO: Getty Images