Felipe Massa was eliminated in Q1 after suffering a loss of power.
Bottas overcame a small hydraulic leak during Q2 to claim his place on the second row of the grid with his final lap of Q3.
Rob Smedley, Head of Performance Engineering: "It wasn't the cleanest session for us on either car. Felipe lost power in Q1 and there was nothing we could do about that. With Valtteri, we had a small hydraulic leak that compromised our Q2, so we were trying to learn about tyre management while running in Q3 and I'm pleased he got to where he did. Now we have to aim to get Valtteri on the podium. For Felipe, we've got to aim to get him in front of one or both Red Bulls."
Valtteri Bottas: "It was a good lap. I would have liked to be ahead of Ferrari but they are a still a bit quicker than us. Fourth is still a good place to the start and now we are maybe the closest to a podium we have been this season so the fight should be fun. This track suits us but it's still difficult to predict how the race pace is going to be tomorrow. If it's good then we can fight with the others around us for a podium."
Felipe Massa: "I lost a lot of power during the session, so we need to analyse what happened with HPP. It's a good track for us and I'm sure we were going to be competitive but unfortunately I could not do anything. At least it's better to have the problem today than tomorrow. Starting the race 17th is difficult but the race is long and in Canada you can get opportunities, so we will try to get as many points as we can."
Williams F1 Team