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Given it it is a works maker of chassis and engine, a status effectively shared in F1 only by fabled Ferrari, Mercedes is being tipped as a true favourite to dethrone Red Bull in 2014.
The W05, now at Jerez for its imminent launch, has already been run at Silverstone for a 40km 'filming' shakedown, and German Rosberg sounded positive on Twitter.
Mercedes' motor sport boss Toto Wolff, however, is cautious.
"It's far too early at this stage to talk about the championship," he is quoted by the German news agency DPA.
Wolff confirmed, however, that the team has been working particularly hard over the winter, with a "night shift necessary every night".