With the four-time World Champion looking uneasy in the new Red Bull, we look at the drivers who could dethrone him this season...
Lewis Hamilton (Mercedes)
The 29-year-old is the early favourite to usurp Vettel and land his second world title after showing impressive form in pre-season testing. After leaving McLaren, Hamilton scored a victory in Hungary, four podiums and five poles on the way to finishing fourth in the drivers' championship.
Fernando Alonso (Ferrari)
Alonso finished 155 points behind Vettel last year in an inferior car, but if Ferrari can get their act together, he will challenge. Last season, Alonso only won two races, but with Kimi Raikkonen's arrival as his teammate, he is under internal as well as external pressure to produce the goods.
Kimi Raikkonen (Ferrari)
Raikkonen's switch from Lotus to Ferrari has prompted much debate about the team dynamic and his partnership with Alonso, but expect the 'Iceman' to live up to his nickname and stay cool under fire. Raikkonen has the reputation of consistency in finishing among the points, which encouraged Ferrari chiefs to bring him in.
Nico Rosberg (Mercedes)
The super-quick German will provide a stern test for teammate Hamilton at the improving Mercedes team this year as he seeks his maiden world title. If Mercedes can keep moving forward after a strong pre-season then Rosberg could be a real contender to emulate his father Keke, the world champion in 1982.
Jenson Button (McLaren)
Button is the grid's most experienced driver but he will be invigorated under McLaren's revamped leadership, headed by arch-competitor Ron Dennis, and has a style well suited to this year's new technical requirements. Button's experience and ability to conserve fuel and tyres will be crucial this year.