Williams head of vehicle performance Dave Robson believes the FW44's performance has been masked by qualifying difficulties this season.
The former F1 constructors' champions saw their momentum from scoring points last year stagnate in the first two races of the campaign with both Alex Albon and Nicholas Latifi struggling to break into Q2.
The former Red Bull driver secured points in Australia and Miami with strong race pace, despite qualifying continuing to be problematic pace-wise.
F1 returns to Barcelona for the beginning of the European season and a chance for teams to measure their improvements from the first pre-season test that was held at the Spanish venue.
Previewing the weekend, Robson said: "The contrast between the new circuit in Miami and the familiarity of the Circuit de Barcelona-Catalunya couldn't be starker.
"The drivers and engineers know the quirks and subtleties of this track very well and, whilst the car balance and tyre behaviour will be different to February, we have a good idea of what to expect and the areas that we will need to work on.
"The car has changed quite a lot since February and the much hotter track conditions will present very different problems."
Addressing the pace of the FW44, Robson added: "We showed some encouraging race pace at the last few events and our efforts are now focused on bringing the same level of performance to Qualifying.
"If we can do this successfully then we will be in a much stronger position going forwards."