Lewis Hamilton said the task of overhauling Red Bull's Max Verstappen to win a record eighth Formula One title felt "as steep as it can be" with four races remaining and 19 points between them.
The 36-year-old Mercedes driver has five wins to his Dutch rival's nine this season, with Verstappen chasing his third in a row in Brazil this weekend.
When asked on November 11 whether he felt Sunday's Sao Paulo Grand Prix was a "must-win", the Briton replied that "every race is a must-win race".
Brazil is expected to favour the Red Bull more than Mercedes, with Verstappen the most recent winner there in 2019 and before the COVID-19 pandemic forced the cancellation of last year's race.
"They've had a strong car all year, they've had the strongest car," said Hamilton. "I think we've done as good as we could.
"Last time here they were incredibly strong so we're anticipating again they'll be very hard to beat this weekend. But where there's a will there's a way, hopefully."
The Brazilian round will also be the third and final sprint event of the season, with qualifying on Friday for a 100km race on Saturday that decides the starting grid for Sunday's main grand prix.
More points are available, with three for the winner on Saturday.
Hamilton said that would be of no benefit if Red Bull were quicker, and anti-clockwise Interlagos was one of the hardest layouts to overtake on.
There has also been speculation that Hamilton could need a new engine, which would trigger a five-place grid drop and further damage his title hopes.
"I can't really comment at the moment. I don't think the engines have even arrived this morning," he said, referring to delays in the freight arriving from Mexico. "As far as I know, my engine's fine. But I'll find out later on."
