McLaren's Lewis Hamilton has conceded his world championship hopes are over after finishing 10th in the Korean GP.
Hamilton dropped down the field following a rear suspension failure - his second in as many races - and is now 63 points off the lead with only 100 still available.
"In terms of winning, I think that's it for us," Hamilton said.
"We were still in the fight up until now but it's too far away. We'll keep fighting in the constructors'."
McLaren have lost second place in the constructors' championship following a poor race in which Hamilton's team-mate Jenson Button was taken out on the first lap by Sauber's Kamui Kobayashi.
McLaren are six points adrift of Ferrari, whose drivers Fernando Alonso and Felipe Massa finished third and fourth in Korea. Red Bull are 77 points ahead of the Italian team following a one-two, with Sebastian Vettel ahead of Mark Webber.
The German's third consecutive victory moves him into a six-point lead over Alonso in the championship.
Hamilton challenged Alonso for third place in Korea in the early laps but began to suffer handling problems and he was told there was a problem with the car. McLaren later said it was almost certainly a rear anti-roll bar failure.
That forced Hamilton to do an extra pit stop because of high tyre wear and his efforts to beat the Toro Rossos to eighth place foundered when he ran off the road and collected some artificial grass which further worsened the performance of his car.
He pointed out that it was the third consecutive race in which he had had a mechanical problem, after retiring from the lead in Singapore with a broken gearbox and suffering a broken rear damper in Japan a week ago.
His frustration with McLaren's performance was clear.
"We had another rear suspension failure somehow, I don't understand how," he said.
And in a reference to his decision to move to Mercedes next year, he added: "It's a day to forget. A year to forget as well. I'm looking forward to a fresh start next year."
Hamilton also hinted that he hoped Alonso would beat Vettel to the title.
"I hope Fernando keeps pushing," he said.
Button said his title hopes were "definitely" over after his retirement - he is 84 points behind Vettel.
"I can't really [remember a worse day in the office]," said McLaren team principal Martin Whitmarsh. "This was one of those days that I won't forget but I will be trying desperately to.
"What we have to do as a team now is say that we have a car that was desperately quick, we can go out there and still get results in these last four races.
"This team is and will be focused on getting out of here as quickly as we can and we'll focus on doing what we can to be there and fighting for victories in the last four races."