Sebastian Vettel has admitted both he and Ferrari need to improve in order to get back into shape to win a world championship.
The Italian team finally looked on track to end a more than decade-long title drought earlier this year, until car and driver problems put the advantage back with Mercedes' Lewis Hamilton.
Ferrari recovered its performance in Austin, but German Vettel admits it is too late.
"We went back to a much earlier version of our car, and it seems to work better that way. It was suddenly easy to drive again," he said.
"But it's never good to have to take a step back with important parts," Vettel insisted.
Vettel himself has also been roundly criticised for a spate of driving errors.
"There are many things that we have to look at in the winter, including myself. I have no problems admitting the mistakes I made," he said.
"I think the crucial factor is that for most of the season we did not have the speed that we would have liked, and this sometimes caused other problems that did not help us," added Vettel.
"In general, we have the potential to do much more, so in some aspects we still have to grow and learn in all aspects."