Williams needs a faster rate of development to not only catch Mercedes and Ferrari but also keep Red Bull at bay, according to engineering chief Rob Smedley.
Substantial progress at Maranello over the winter propelled Ferrari above Williams as the team closest to Mercedes, a role the Grove outfit held for much of 2014. Williams has been comfortably third in the pecking order at the opening four races of the current season, though Valtteri Bottas managed to hold off Sebastian Vettel to finish fourth in Bahrain.
Head of performance engineering Smedley is happy with what Williams has been able to extract from its current package but is under no illusions a big improvement is needed to catch the leaders.
"We've had four races now and it's quite clear what the order is," he said. "We've got some upgrades coming for Barcelona. I think it will be a fair old challenge to catch [Ferrari] back up, especially in terms of race pace, by Barcelona, but the target is that we'll catch them back up."
"I think that we're optimising fairly well the package that we've got now. There's more to come, but not huge chunks from what we've got. But we need to develop the chassis, or the whole car package, faster and at a higher rate if we want to catch the people in front - and our primary aim is to catch the people in front."
Red Bull has had a troublesome start to 2015 and is yet to finish higher than sixth, due in part to ongoing problems with its Renault power unit, but Smedley feels it would be wrong to overlook the former world champions.
"We always have to bear in mind we've got a huge organisation which is very technically able in Red Bull behind us who will eventually get their act together and be a lot stronger than they are now. We need to be looking forward but keep an eye on what's going on behind us as well. We're dealing with massive teams, very well organised teams, Ferrari in front, Red Bull behind, and that's the playing field we're looking at."