In the race, Massa was punted out at the first corner while Bottas finished sixth, fighting through the pack after hitting the wall and damaging his wheel.
Pat Symonds says the Finn should thank former team driver Pastor Maldonado for the robustness of the car's suspension.
"Our suspension is very strong," Williams' technical boss told Auto Motor und Sport. "Pastor pushed the limits very often in the past and that probably had an influence on the design."
Symonds said that if Massa and Bottas had clean races, they would have set their sights on the podium.
Former F1 driver Mika Salo told the Finnish broadcaster MTV3: "Williams' car is the second fastest after Mercedes."
According to Turun Sanomat newspaper, Mercedes chief Toto Wolff agrees: "If their weekend had gone normally, most likely they would have been driving for the podium."
Asked if Williams can now challenge every single team except Mercedes, Symonds insisted: "I want to beat Mercedes as well.
"Our view is that Mercedes is at the front, and then there is a group of cars and we feel that in optimal conditions, we are narrowly at the front of that group."