Valtteri Bottas pointed to the excessive wear of his soft compound tyres as the reason why he could not defend his position against Sebastian Vettel in the closing stages of the US Grand Prix.
A thrilling finale in Austin saw Lewis Hamilton pressing Max Verstappen for second place with just a handful of laps remaining.
Had the Mercedes driver succeeded in passing the Dutchman, while Bottas fended off Vettel for fourth, Hamilton would have sealed the title.
Ultimately however, both Mercedes drivers lost out in their respective battles.
"I think it was about five laps too many for my tyres," said Bottas who was passed by Vettel two laps from the checkered flag.
"I told the team, maybe three laps from the end, that the tyres were suddenly starting to go and I was struggling in all the corners for traction.
"I tried to defend but he [Vettel] had just better life in the tyres and pulled more than five seconds in just one and a half laps, so it was pretty tough in the end.
Bottas admitted to being surprised by the difficulties he encountered with Pirelli's soft rubber.
"For me the supersofts worked well in the first stint and once people started stopping I was feeling comfortable with the tyres," he added.
"Initially I had some problems with overheating but then it was getting better and better. As the tyres were wearing we could push a bit more and even with the supersoft it was good.
"Obviously the soft was always going to be unknown. Normally it has been the better tyre on the long runs but today, for some reason it didn’t quite work."
Earlier in the race, the Finn was ordered by Mercedes to yield to Hamilton twice, once after the VSC period and then later when the Brit found himself behind his team mate after his second pit stop.
"I would have been happy for him [Hamilton] to win it here," said Bottas.
"Obviously I was trying everything I could, I lost myself two or three seconds every time I had to let him by, so for sure that compromised me a little bit. But maybe he’ll win in the next one."
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