Three former drivers defend Vettel
But Timo Glock told Speed Week that writing off Vettel, 32, as a has-been is "too extreme".
"He is in a dry spell and needs to wait until it stops. Maybe things are not the way they should be at Ferrari," the former Toyota driver added.
Asked if leaving Ferrari could fix the quadruple world champion's issues, Glock answered: "Yes, I think so. We've seen it in the sport many times before.
"Maybe it would do him good."
"Sebastian has never liked pressure," he told Auto Bild. "He has it at the moment, but he will come out of it too."
Berger advises Vettel to "keep your nerve, press the throttle and do not read any newspapers".
As for whether Vettel should quit Ferrari, he added: "Sebastian has to look for where he feels comfortable.
"There are some who can deliver whether they are comfortable or not. And there are some like Sebastian who need to feel good," said Berger.
Berger knows Ferrari well, having raced for the Maranello team in the 80s and 90s. He said: "You can feel extremely comfortable there, but there are times when you feel extremely uncomfortable.
"Vettel is currently in the uncomfortable phase."
Another former F1 driver, Ralf Schumacher, blames Ferrari for Vettel's situation.
"The car is clearly difficult to drive, so they need to support Sebastian when he makes mistakes that happen under pressure.
"He has not suddenly become a bad driver," Ralf added.
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