Sebastian Vettel is "no longer among the best" because of Ferrari, Red Bull advisor Helmut Marko claims.

A number of mistakes in recent years has seen increasing scrutiny on the four-time world champion as he has come up second best against Lewis Hamilton and this year saw his lead driver status threatened by Charles Leclerc.

His diminished star means most expect Vettel to retire after next season and Marko, who oversaw his rise through the Red Bull program, blames it solely at the environment at Maranello.

"Unfortunately, I have to say that he is no longer among the best," the Austrian told Motorsport Total.

"He was spoiled by Red Bull because we always spoke honestly with one another. Ferrari is known for politics within the team, and maybe Sebastian is a bit too honest.

"Perhaps, also, it came as a surprise to him how fast Leclerc is."

At the same time, Marko still has faith in the 32-year-old.

"Don't write him off just yet," he added.

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Another element Vettel has had to overcome at Ferrari is the burden placed upon them to succeed by the Tifosi, who have now gone 11 years waiting for a championship.

“Simply, the fans don’t know that, to reach a high level of performance, you need time,” former Ferrari chief and current McLaren performance director Andrea Stella told AutoMoto.

“You need two/three years of work for the reliability and you need five years of research.

“Ferrari have great people, the same equipment, the same availability that I found here in the UK.

“The difference is that in the UK it is only a job. When I finish work, I go out of the office and go to the bar, maybe meet people from other teams and have a chat then go home, maybe the staff knows I am working in Formula 1 but they don’t care.

“When I was in Ferrari it wasn’t a job, it was a mission that completely absorbs you. When I finished working, I was going to the bar and the barista would ask me ‘so Ferrari…are we winning this year?’

“You would go to the restaurant and the waitress will stop you and ask ‘are we winning this season?’ You would open the newspaper and every morning there was an article on Ferrari.

“In Maranello, you never switch off, it’s not a job it is something else completely even if the actual work is just the same.”