Williams' technical boss Pat Symonds has suggested that catching up with Ferrari at the Italian Grand Prix could be difficult, but "not impossible".
However, Symonds has admitted that he is disappointed not to be nearer to Ferrari in terms of performance.
He told Formula 1's official website: "We are in a position where we pretty much expected to be. I had hoped that we would be a little closer to Ferrari, but I know that they've had quite a good engine upgrade – and more power helped them quite significantly on this circuit.
"We know where we are relative to Mercedes. When we don't perform very well, as in Spa, we find Lotus, we find Red Bull and we find Force India close to us – and I don't like that situation. We've got to be in front of them – and here we are.
"We are back to our normal place. So the reading of today is: we are back to situation 'normal'! And all indications show that we should have a very good race. Improving our position and fighting with the Ferraris will be difficult - but not impossible!"
Williams are third in the constructors' championship.