Vettel has suffered a pretty horrendous start to the 2019 season - without a race win - after being controversially denied after a collision with Lewis Hamilton in Canada recently.
Ferrari veteran Mazzola - who was head of the team's testing side - during its golden era, has said that Vettel does not seem to be at the end part of his career just yet but has admitted the difficulties the four-time world champion is currently facing.
"I do not agree that Seb is a driver at the end of the line in his F1 career. Yes, he is facing very real difficulties," Mazzola told Turrini.
Charles Leclerc has provided Vettel with some real competition this season and has been in the much better form over the last few races. Leclerc isn't the only problem for Vettel, though, according to Mazzola: "Obviously not, there is more (problems). The car.
"I'll explain: it is clear that the technical features of the SF90 is not suitable to Vettel's driving style. The car is unstable, taming it is not easy. Seb has a different sensitivity to that of Leclerc.
"I add another thing, even when he had (Kimi) Raikkonen beside him, the German sometimes had more trouble than Kimi to understand the car. This is nothing strange, they are dynamics that are part of a driver's make-up."