Lewis Hamilton is right to warn that you can never be complacent when it comes to sealing a world championship. He stands on the brink of being crowned for a fifth time, but knows better than anyone that you can't relax until you know it's signed, sealed and delivered - just look at what happened in 2007, when his seemingly impregnable lead evaporated in China and Brazil.
Sebastian Vettel has no chance of winning the world championship - it would be far more improbable even than Kimi Raikkonen's '07 turnaround - and he'd be on the back foot even if he wasn't 67 points behind. While the terrible weather that hit Austin during Friday practice means we had no chance to evaluate the relative performance of Mercedes and Ferrari on the day, the previous three weekends have proved emphatically that the silvers cars are the faster by some margin.
While Ferrari has brought a floor upgrade to Austin that could change things, its form over the past three races at three different circuits paints a very consistent picture of the performance deficit in qualifying. On average, Vettel has been 0.612% off in qualifying. This translates to approaching seven tenths of a second over a lap of Austin - more than even a substantial floor upgrade is likely to produce. Even though the gap isn't as big in the race, that still puts Ferrari a step behind Mercedes.