Lewis Hamilton's former teammate Nico Rosberg says both Sebastian Vettel and Valtteri Bottas have the potential to challenge the world champion this year.
Rosberg beat Hamilton to the title in 2016 before retiring from the sport as champion at the end of the year. Bottas replaced Rosberg at Mercedes but for the last two years Ferrari's Vettel has been Hamilton's closest competitor.
Rosberg believes Vettel is under intense pressure to mount a successful title challenge but says he is capable of getting the better of Hamilton over the course of a season.
"The pressure is on, absolutely," Rosberg told Sky Sports.