Williams still unsure on qualifying pace

The team felt that they had under-performed with their single lap pace in Australia, and changes made to the car for Sepang appeared to indicate an improvement as Nico Rosberg took sixth place on the grid.

But technical director Sam Michael remained cautious as to how much progress the team have made, because he thinks the warmer weather in Malaysia played into their hands.

"In the (pre-event) test we weren't sure if we had made enough progress on it because we looked like we were quite strong on long runs, and maybe not as strong over the first lap," said Michael, who saw Rosberg's race end with a mechanical failure 13 laps from home.

"But here two things helped around Malaysia. It is very hot and it is a very abrasive track. The track is very abrasive so there is a lot of energy.

"Although we had a reasonable qualifying performance with Nico, if the track temperature goes down and it gets cold then I am not sure we have really got on top of that yet.

"We haven't been able to do any testing in cooler conditions because it was still 50 degrees Celsius on the track during the test.

"Getting the first lap has never been an issue here really, so while we did get on top of it in Malaysia I am not sure how much of it was just turning up a different circuit that is very hot."

Williams are still unsure about the exact cause of Rosberg's retirement, with investigations continuing at their Grove factory and at engine provider Toyota's factory in Cologne.