Williams were "surprised" by their Friday practice pace after Valtteri Bottas and Felipe Massa finished 'best of the rest' behind Mercedes in third and fourth, albeit half a second adrift of Lewis Hamilton.
The Grove outfit are locked in a close battle for fourth place in the championship standings are currently sit fifth, nine points behind Force India.
Head of performance engineering Rob Smedley believes the hard work they've done behind the scenes paid off on Friday and reckons they're in "good shape" this weekend.
"We are pleasantly surprised at how good our pace was today. We’ve done a lot of set-up and development work in the simulator, and then subsequently on the track here, and the drivers are happy with the results," he said.
"We knew we had to take a slightly different approach for a track like this, with the low-speed corners, so that’s what we’ve been concentrating on.
"Both the low and high fuel runs looked good, we could run the soft tyre easily as long as we need to, and it was good on the medium tyre as well. There was a lot of degradation on the high fuel, but the degradation was high today so the aim is to have relatively less than other people, overall we’re in good shape."
This race will be Massa's last in front of his home crowd and he is confident of carrying Friday's pace over to Sunday.
"It’s definitely been a good day. It’s always nice to see your name near the top of the leaderboard. I’m really looking for that competitiveness tomorrow and especially on Sunday.
"This is a track that I love and the people here really support me, which gives me so much more confidence. I hope we can stay up there this weekend. It won’t be easy but I will definitely try!"
