Following the Mexico Grand Prix, Mercedes driver Lewis Hamilton was crowned champion for the fifth time, despite finishing fourth.
His performances earlier in the season secured him with the well earned fifth title.
Sebastian Vettel, however, finished second in this particular race, and reflects a season that was nowhere near his best for the Ferrari driver.
According to former F1 driver Sir Jackie Stewart, it is only downhill from now for Vettel, who Stewart says is "past his peak".
The German driver has won the title four times, but being unable to finish above Red Bull's Max Verstappen in Mexico meant his rival Hamilton was crowned champion.
The German driver has made a few costly mistakes this season, and Stewart takes that as a sign Vettel is past his best.
"I think Sebastian is past his peak and Lewis is still building to his," Sir Jackie told Bild.
"There's no reason Sebastian cannot come back, but it will be very difficult because after a season like that, you are more critical of yourself, and what you want to do and what you don't want to do."
Stewart allured to a few times Vettel crashed this season by not making the right move, or at the wrong time.
"It's not possible to keep blaming everyone else. If you fight for a world championship and you see that a move you make could be a problem for you, you don't necessarily try it. You wait for the right moment."
Vettel joined F1 at the age of 20, and had won four championships by the time he was 26, and Stewart gave an insight into why Vettel could have dropped in form.
"I like Sebastian very much and he is a very good driver. Very emotional, and technically maybe still the best, but he does not have clear mind like he used to."
With a couple Grands Prix still to come, perhaps Vettel will finish on a high, and place first in at least one race.
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