F1 returnee Jacques Villeneuve reckons that fitness could be the key to a strong result in Malaysia next weekend, as it can be 'very, very hard physically'.

Speaking as the clock ticks towards round two, Villeneuve, who was far from impressive in Australia, knows that he will need to do better if he is to avoid more criticism.

"Sepang is a good circuit but it's very difficult," noted the Canadian.

"It's got a lot of interesting corners, both high-speed and low-speed, and it's quite a long lap.

"Malaysia is also very, very hard physically. This is the first hot race of the year and all of the winter testing is usually done in relatively low temperatures, so it's quite a shock to the body.

"It is also hard on the car, and cooling the engine and brakes is even more critical. Sepang is always a difficult race."

Sauber team-mate, Felipe Massa also agrees that it is far from easy.

"Sepang is very tough physically because of the humidity," added the Brazilian.

"You sweat an awful lot and can lose 2 to 2.5 kg over a race distance. That's going to be made even tougher this year on the mental side by the need to look after your tyres, especially during the closing laps.

"Despite this though, I love the Sepang track. There are a lot of fast, flowing corners where you can get a really good rhythm, and there are a lot of opportunities for passing, especially if you get a good tow down the two long straights.

"I think we could see a lot of overtaking this year, and the change in downforce rules will help."