And the Grove based team's next target is Force India, according to top engineer Rob Smedley.
"The glass is more than half full," Smedley, who switched from Ferrari at the end of last season, was quoted by Germany's Auto Motor und Sport on Sunday.
"Our car is now third fastest (in 2014)," he insisted, referring to dominant pacesetters Mercedes and reigning world champions Red Bull.
Driver Felipe Massa, who also moved from Ferrari to Williams to 2014, agrees with his former race engineer and friend Smedley, predicting the British team can now hold off grandee McLaren's charge for the rest of the season.
"We can fight against Force India and McLaren," he is quoted as saying. "Against Ferrari it will be harder, because they have more resources, but it is not impossible."