Lewis Hamilton says he is taking nothing for granted in the title race despite opening a huge lead with victory in the Japanese Grand Prix.
The Mercedes driver leads Sebastian Vettel by 59 points after his Ferrari rival retired early in Suzuka.
"I just have to keep my head down and keep doing what I've been doing," Hamilton said. "There are still 100 points available.
"We've still got to win the next four races."
Hamilton has taken four wins and a second place in the five races since Formula 1 returned from its summer break at the Belgian Grand Prix at the end of August.
By contrast, Vettel's bid has imploded, with a start-line crash in Singapore followed by engine issues affecting his races in Malaysia and Japan.
Hamilton will clinch the title if he wins the next race, the US Grand Prix in Austin, Texas, and Vettel is lower than fourth.
Hamilton said: "Is it a purple patch? A golden patch maybe. It's definitely been a great second half of the season. An incredible performance from the team."
Hamilton said his advantage was "kind of unbelievable, really", adding: "I could only have dreamed of having this kind of gap. Ferrari have put on such a great challenge all season long. My team have done a great job. They are so meticulous and that is why we have the reliability we are having."
Vettel suffered a problem with a spark plug which cost him power and the team retired his car after four laps.
The problem comes a week after he started from the back of the grid in Malaysia after a failure in a manifold in the engine in qualifying, an issue which also caused team-mate Kimi Raikkonen's retirement before the race started the next day.
Vettel admitted that winning the championship would now be difficult.
"Of course," he said. "I don't have to be a mathematician. What we have to do now, and I said also to the guys: 'Let's get back, get some rest. It has been tough weeks with a lot of changes.
"The mechanics are tired, the team is tired. It is good to get some rest and then we know we have the package to do well in the last four races. That's what we focus to do and the rest we'll see."
Mercedes F1 boss Toto Wolff said: "This is a sport where you take no prisoners and reliability is part of making it to the end and we have been there in the last few years.
"We just need to collect the points but I can relate to how it feels for Ferrari and it is certainly not very nice.
"It is not over until it's over. We have seen with Sebastian's misfortune how quickly you can lose points. It is all about finishing the races.
"There are 100 points left. We just need to look one race weekend after the other and score. Austin can be a solid step towards the championship but we won't be counting our chickens until it's done."