Ferrari criticism this season unfair - Vettel

Mercedes clinched its third-consecutive constructors' title at the last grand prix in Japan, where Ferrari felt it had regained the upper hand in terms of pace over Red Bull.

Is the Vettel-Ferrari dream heading for failure?

Ferrari, however, has fallen 50 points adrift of Red Bull in the battle for second, leaving the critics to bemoan to how far it has fallen behind Mercedes, talk Vettel feels is unwarranted.

"If you look at the gap to Mercedes it has been fairly stable," he said.

"Some races we are a bit closer, some races we are a bit further away.

"It is fair to say that in qualifying the gap is big and in the races it shrinks a bit, but it's still there.

"At the start of the year we were clearly the second best team, but now towards the end of the year, here and there in terms of pace, we slip behind. I think it's very close.

"But it's not that fair to say we are massively behind - a tenth-and-a-half [of a second] is not big.

"Fair enough, we are obviously level with Red Bull and it will be our target to get second in the constructors' [championship] back."

Ferrari has also come under fire for appearing to lose its way behind the scenes, notably parting company with technical director James Allison in July, and then changing its technical structure.

Team principal Maurizio Arrivabene recently claimed the new line-up was working, and that progress was being made, even if the team had "failed on matching our targets we set this year".

Vettel also recognises that has been the case, with Ferrari without a pole or a win this year, but is convinced the team did the right thing in sticking to its principles.

"We came into this year with high expectations, but we had to learn that we are not achieving what we set out to achieve," said Vettel.

"Arguably we had a lot of races that didn't go according to plan, but I think as a team we never lost focus.

"So even if there were a lot of things that people called bad luck, or whatever, I think we stuck to our way and that was the right thing to do. We are still heading in the right direction.

"Sometimes you wish results would come and confirm this - sometimes they do, sometimes they don't, but the most important thing is that they do, and I believe they will."