Williams has admitted it will struggle to quickly recover its position as the first force behind title favourite Mercedes.
The Grove team finished last season as clearly the fastest team behind the title winners, but the fabled Italian giant Ferrari has sped past in 2015.
“After the first four races you can already see the balance of power,” chief engineer Rob Smedley said after the Bahrain grand prix.
“We are preparing a series of upgrades for Barcelona, but catching up with Ferrari will be very difficult.”
Team driver Felipe Massa acknowledged in Bahrain that Williams’ much smaller budget against the might of Ferrari is beginning to show.
“Third isn’t anything to be ashamed of,” Williams deputy Claire Williams told Britain’s Sky.
She agreed with Massa that competing against Ferrari’s spending is difficult.
“I’ve always said it’s about working harder and smarter than the others,” said Williams. “The likes of McLaren and Ferrari have always had bigger budgets than us and we have won sixteen championships against them.
“I heard that Ferrari are ploughing in another 100 million to their development on top of what they had already allocated — and that’s our whole budget!
“To be honest, I’d love to be able to win against them,” she smiled, “with a third of their budget.”
But from an engineering perspective, Smedley acknowledged how hard it will be for Williams to fend off his and Massa’s red-clad former employer.
“We have already extracted good potential from our cars,” he said, “and this work continues, but we do not expect to be able to rapidly increase our pace.
“Also, we can’t forget that behind us there are teams like Red Bull, which is a huge organisation, well equipped and with a very considerable resource.
“When they sort out their problems,” said Smedley, “they will be doing much better than they are doing now. Generally, all of our main rivals are very strong.” (GMM)