Formula One's top drivers were up early Sunday making anxious checks on the weather ahead of the season-ending title showdown between Sebastien Vettel and Fernando Alonso at the Brazilian Grand Prix.

Spain's two-time champion Alonso of Ferrari was the man with most to gain, or lose, in wet or dry conditions and, like most neutrals and hordes of local tifosi, was hoping for rain to reduce the performance advantage of Vettel's Red Bull.

With just one race of 71 laps around the spectacular old Interlagos track built between two lakes to decide the season, Alonso has to close a deficit of 13 points on the German to take his third title.

By contrast, championship leader and defending champion Vettel needs only to finish in the top four to be sure of doing the same and becoming the youngest triple champion in history.

Indeed, whichever driver wins the title -- Alonso, at 31, or Vettel, at 25 -- will take that record too.

For Alonso, reliability is paramount. Even if Vettel falls victim to an accident or a mechancial failure, he still has to score a podium finish to make up his shortfall in points.

But whatever the outcome, he believes he and his Ferrari team have already done enough in 2012 to fly home from Sao Paulo filled with pride.

"If I had done a standard championship then I would have something like 110 points now and I would have said goodbye to the championship around Hungary or Singapore," he said.

"I would then have done the last races with no pressure, like last year, when I was not fighting for anything. Luckily, having had an abnormal championship has taken us to have the feeling that here it's all or nothing.

"Probably for the fans it will be a big joy or a big disappointment and it's understandable. But for us it has to be a prize if we achieve it and if we don't then we should be proud of having done our job in the best possible way."

As Alonso reflected philosophically on the season past and the race ahead, without giving any signs of tension or stress, Vettel was on Saturday night in Sao Paulo busy quashing all suggestions that he is finding the pressure difficult.

Having secured fourth place on the grid with a below-par performance in qualifying on Saturday -- his worst effort since the Italian Grand Prix in early September -- the champion reacted testily to a suggestion, from pole-sitting Briton Lewis Hamilton of McLaren that 'you could see with Sebastian that the pressure is on him'.

"No, to be honest," said Vettel. "I did a mistake in the first run of Q3 but not because this is the last race or whatsoever. I'm pushing and that's what I try to do all the time. I did a mistake, lost quite a bit, I went wide, lost momentum and more than half a second was gone.

"The first run wasn't clean, so I thought I had one run left and it was quite important to make sure I get a decent lap. It wasn't the lap of my life, I have to admit.

"If your first run is all pukka, then you might as well drop your pants in the second run and see what you get."

Few doubt that with Hamilton leading a McLaren front row lockout with team-mate and compatriot Jenson Button alongside him, the real focus of the action will be behind them as Alonso seeks to climb from seventh to try and pass Vettel.

Vettel has the speed, but Red Bull have shown they can be vulnerable and inconsistent. And in Sao Paulo, where the rain can sweep across the circuit and play havoc with all advanced planning, anything can happen.

Sunday will also be an emotional day for seven-time world champion Michael Schumacher who will head into retirement having qualified in 14th place on Saturday.

The 43-year-old German is not going quietly, however, claiming his Mercedes team compromised his car set-up too much in qualifying in the hope that it rains on Sunday.

"We might have compromised the car too much for the rain which is expected for tomorrow and was also forecast for qualifying," he said.