Williams are not entering 2016 targeting another third-place finish in the constructors' championship.
That is the view of Felipe Massa, who alongside Valtteri Bottas helped the Grove team beat giants like Ferrari in 2014 and Red Bull last year.
"For the size we are, Williams did a very good job in the last two years," Massa told Sportv programme Ta Na Area.
"On the financial side, we are lower than Mercedes, Ferrari, Red Bull and McLaren, but now we are working harder to get closer to them and maybe have a chance to win again."
The 34-year-old also told Brazil's TV Globo: "The work is always to fight for the title. We have to put our feet on the ground as the others are also working hard, but I believe this will be the year where Williams will improve the most.
"Seeing the car, I notice that we have many new things, so we will try to close the gap to Ferrari and even Mercedes.
"I hope we can fight for victories and even the championship."
Williams finished 2015's constructors' championship, in third place with 257 points to the 703 of winners Mercedes.
