Felipe Massa is expecting a "big fight" with Ferrari in the Australian GP after qualifying concluded with third to seventh separated by four-tenths.
While Mercedes comfortably secured the front row of the grid in Melbourne on Saturday, Williams had a close battle with Ferrari.
Massa emerged victorious in that to finish best of the rest ahead of Sebastian Vettel.
However, it could have gone either way as Massa was a mere 0.039s quicker than Vettel while Kimi Raikkonen was a further 0.030s back.
In fact the gap between the Brazilian and his team-mate Valtteri Bottas, who was seventh quickest, was only 0.369s.
"It was a very tricky qualifying, especially when you have four cars fighting for similar time all the time.
"The difference in lap times between me, Sebastian, Kimi and also Valtteri it is pretty small.
"But I'm happy, I'm happy that I did a good lap.
"It was the best lap of the day, the last one, which is not so easy especially with the wind changing so it was easy to have front locking in the corners.
"Maybe I just prepared everything for the last try and it worked, it worked pretty well."
As for Sunday's grand prix at the Albert Park circuit, the Brazilian is expecting Williams will be pushed all the way by Ferrari.
He added: "It will be a big fight tomorrow with Ferrari especially but I hope we can do a good job."