Lewis Hamilton all but ruled out his chances of competing for a record eighth world championship in the next two years after Mercedes' "inexcusable" performance at the Brazilian Grand Prix on Sunday.
Max Verstappen won his 17th race of the season, extending his dominance in Formula One, while Mercedes had a terrible afternoon.
Hamilton finished eighth, 63 seconds behind the winner, while Russell was forced to retire his Mercedes.
The previous two races had given Hamilton and Mercedes hope that they were closing in on Verstappen's Red Bull team.
Armed with a new floor, Hamilton finished second in Austin, before he was disqualified after his Mercedes failed a post-race scrutineering check. He was runner-up again in Mexico seven days later, this time with a legal car, 14 sec adrift of Verstappen.
But the Silver Arrows were dealt a grizzly reality check here.
Far from being any closer to Red Bull, Mercedes were slower than McLaren, Aston Martin, Ferrari and the mid-table Alpine team, with Pierre Gasly embarrassing the former world champions when he batted aside Hamilton and Russell.
Hamilton admitted after Saturday’s sprint race – where he laboured to seventh, 35 seconds behind Verstappen – that he was counting down the days until the end of the season.
Twenty-four hours later he expressed his fear that he will not be in a position to take on Verstappen before his £100million two-year deal expires at the end of 2025.
Hamilton, 39 in January, said: “All I can do is try to remain optimistic. But the Red Bull is so far away, they’re probably going to be very clear for the next couple of years.
“I knew it would be a tough one. In the moment, it is a setback. But as a team we will just come together and try to push forward.”
Mercedes team principal Toto Wolff could not hide his despair at the result.
“An inexcusable performance,” the 51-year-old Austrian said.
“There are no words for it. The car finished second last week and the week before and whatever we did to it was horrible
“Lewis survived out there. I can only feel for the two driving. It is a miserable thing. The car is on a knife’s edge and we have to develop it better for next year because in seven days you cannot have one of the quickest cars (in Mexico) and then you are nowhere.
“The car almost drove like it was on three wheels and not on four. This car doesn’t deserve a win.”
The start had been mildly encouraging for Hamilton. The seven-time world champion started third, up from his grid spot of fifth, when the race resumed after Alex Albon crashed into the wall and his loose tyre narrowly missed striking Daniel Ricciardo on the head.
But Mercedes’ abject pace was soon laid bare for all to see. Fernando Alonso wasted no time in racing past Hamilton at the Curva do Lago on lap four.
With Russell one place behind Hamilton, and having no luck in calling on Mercedes to move his team-mate out of the way, the black-liveried duo started tumbling back through the field.
Aston Martin’s Lance Stroll and Ferrari’s Carlos Sainz made light work of the two Englishmen. Gasly was next, leaving Hamilton in eighth and Russell one place back. Russell was then told to retire his car with an engine failure 12 laps from the end.
Hamilton now trails Perez by 32 points in the race for runner-up in the championship after the Red Bull driver failed to take the final spot on the podium.
Perez got ahead of Alonso on the penultimate lap only for the Spaniard to blast back past the next time round. The two drivers then went toe to toe on the 200mph drag to the chequered flag, with Perez finishing just 0.053 seconds behind.
Lando Norris took second, following another fine drive. He even threatened Verstappen for the lead on lap eight before the Dutchman reasserted his authority
The 26-year-old’s latest triumph ensures he will end the year with the greatest win ratio ever seen over a single season.
Verstappen has won 85 per cent of the races, and with just rounds in Las Vegas and Abu Dhabi to follow, he will post a greater one-campaign ratio than Alberto Ascari’s 71-year record which stands at 75 per cent.
