Rosberg on Ferrari-decline: You have to be "perfect to beat "war machine" Mercedes

F1 world champion Nico Rosberg has shown his sympathy for Ferrari's recent decline in the title race, as the German explained that in order to beat Mercedes, you have to be absolutely perfect.

Rosberg, who retired from Formula One only days after winning his first title in 2016, was a Mercedes driver for a big part of his career, teaming up with current championship leader Lewis Hamilton for three years. He won the constructors' championship three years in a row with the Silver Arrows, so he knows all about the strengths of the team.

"The fact is that Mercedes is a war machine," Rosberg told Gazzetta dello Sport.

"I mean, the whole package is; the car and Lewis Hamilton.

"To beat them, you have to be perfect, and Ferrari hasn't been able to be [that].

"But at the end, it's not strange [that Mercedes is winning]; 

"At Mercedes, the team has been more or less the same for five years, and there have been so many changes at Ferrari - it takes time to get the maximum out of the team."

That is true in a way. Ferrari team principal Maurizio Arrivabene has only been there for four years, Vettel's only been there since 2015, and so has a large part of the engineering crew. Is that the reason why they can't quite maintain the level at which Mercedes is at, or do you think something else is at play here?