But now he says: "With Ferrari performing, there is no reason for him to not stay."
Indeed, quadruple world champion Vettel has won two of the three grands prix so far this year, and is leading the championship from Mercedes' Sebastian Vettel.
"Of course, if there is a stretch where he doesn't win any races, there will be enormous pressure," Berger told the German broadcaster Sky.
"But it looks at the moment that they are on the right track. I cannot imagine anything changing," the former Ferrari and McLaren driver added.