Valtteri Bottas says the latest Williams updates worked well in practice for the Chinese Grand Prix, and the Finn believes that the team can fight with Ferrari in qualifying.
Bottas finished second practice in seventh place, behind the Ferraris of Kimi Raikkonen and Sebastian Vettel, but he remains confident that there is more to come.
"We tried some mechanical changes as well as new aero updates," he said. "Everything seems to work as expected, and that's always nice to see.
"The car felt a bit better than in Malaysia. The long runs were also a bit more consistent."
He stressed that it is important to focus more on readying the car for the race, and in particular optimising tyre usage.
"I think whatever we are going to do now with the car set-up, it should be for the race.
"I know in qualifying we should be reasonably strong, we can definitely fight with Ferrari in qualifying, I think.
"But whatever we do, we need to make changes for the race – especially to save the front left tyre, which for everyone seems to be the main issue."