Jenson Button believes Lewis Hamilton will beat Mercedes team-mate Nico Rosberg to the Formula One title if the Brazilian Grand Prix is in wet conditions.
Hamilton topped both practice sessions in Sao Paulo on Friday in what is the penultimate race of the season.
But while Rosberg holds a 19-point lead in the drivers' standings, rain is expected to play its part during Sunday's race.
Button, the 2009 world champion, feels wet weather would suit Hamilton, and prove decisive in the title race.
"If it's wet here, I back Lewis for the title, if it's dry, Nico," the British McLaren driver said, via The Guardian.
"I think the idea of a wet race will worry Nico and then the pressure is there, definitely. I qualified 14th in 2009. It was wet and I thought any little movement would be disaster. One little slip is enough to cost you a second, or you put it in the wall.
"Mercedes are that good a bad result for them is second but if it's wet it definitely mixes it up.
"I think the Red Bulls will be very strong in the wet. Power doesn't matter so much then. It could be really exciting."
Rosberg has won the past two races in Brazil, and he was third and second in the respective practice sessions on Friday.
A win on Sunday would secure the German his first F1 title.