McLaren's 2007 Formula 1 title meltdown plays on Mercedes' mind

A run of four consecutive victories for Lewis Hamilton has left him 67 points clear of Sebastian Vettel in the drivers' standings, with only four races remaining.

If he wins at Austin this weekend, with Vettel no higher than third, that will be enough for Hamilton to claim his fifth world title.

But Wolff fears there is always the prospect of something unexpected happening - and he cites 2007 as a classic example.

Back then, under the old points structure, Hamilton held a 17-point advantage over Kimi Raikkonen with just two races of the season to go - meaning he just needed one third place to claim the title.

But a crash on the way into the pits in China, and a gearbox problem in the final round in Brazil, left the door open for Raikkonen to take the crown.

Speaking about the impact of the sizeable advantage Mercedes has heading into this weekend's United States Grand Prix, Wolff said: "It doesn't change anything. In 2007, two races to go, 45 points in today's points, and [Lewis] lost the championship.

"Would anybody ever have thought that you could lose 45 points in two races? Impossible.

"Racing happens on Sunday, and not necessarily the quickest car wins.

"We had a moment in the summer where we weren't the quickest car, and we scored some victories.

"I wouldn't want to take the foot off the pedal because a DNF and a freak race, and it's all vanished."

While Mercedes has worked hard since its defeat in the Belgian GP to ensure it has maximised its opportunities, it acknowledges there is little it can do to avoid "freak" circumstances coming into play.