Valtteri Bottas has said that it is too early to become overly disappointed with the pace of Williams's 2016 car.
The Finn finished just eighth in Australia, having qualified in the midfield.
"It is difficult to say much about the pace in qualifying as I didn't get any clear air and then I got the [gearbox change] penalty, but it is clear that we need to improve relative to the fastest cars," he is quoted as saying by Turun Sanomat newspaper.
"We are not satisfied with where we were in Australia, but we will see how we go in Bahrain, where we will have new parts on the car."
The centrepiece of the Bahrain upgrade is a new ultra-short nose, but it is believed that will actually only be fitted to teammate Felipe Massa's sister car.
