Gerhard Berger believes that Ferrari's resurgence this season has led to momentum which Sebastian Vettel can carry all the way to the world title.
After trading wins with Lewis Hamilton in Melbourne and Shanghai, Vettel gained a clear upper hand last weekend in Bahrain, a state of affairs which has surprised Berger.
"I would have lost every bet before the season," the former Ferrari and McLaren driver told Sport Bild.
"Because I doubted that Ferrari would really beat Mercedes. The Vettel factor can decide the world championship this year."
Berger also believes that Vettel's early form bodes well for the Scuderia's chances of keeping the German on-board for 2018.
"With Ferrari performing, there is no reason for him to not stay. Of course, if there is a stretch where he doesn't win any races, there will be enormous pressure.
"But it looks at the moment that they are on the right track. I cannot imagine anything changing."