However, his US Grand Prix weekend started poorly on Friday.
"It was a bit confusing today," the German said.
La Gazzetta dello Sport reports that, after a spin, the decision was taken to change Vettel's chassis ahead of qualifying and the race in Austin.
"We are not worried," Vettel insisted. "The car is fast. For sure Mercedes is too but as I said we are not worried, we just missed a few laps compared to them.
"Let's take the situation as it is and try to make sure that on Saturday the car is quick."
German F1 broadcaster Sky reports that the consequence of Ferrari's collapsed title chances due to poor reliability is that team boss Arrivabene will lose his job.
Technical boss Mattia Binotto is tipped to replace him.