Valtteri Bottas is adamant Williams can do an "awful lot better" in the 2016 Formula One season.
Williams finished third in the constructors' championship, 70 points clear of Red Bull.
The British manufacturer had four podiums for the season - two for Bottas and two for team-mate Felipe Massa.
And Bottas is expecting Williams to be even more competitive next season and try to close the gap to Ferrari and Mercedes.
"It is possible but I have always said that it is difficult," Bottas told Autosport.
"It is very competitive at the moment and the rules are not changing massively for next year.
"Mercedes and Ferrari have a pretty good base car even though it is a development so it's tricky.
"But I think we can do an awful lot better than what we are seeing this year .
"If all the work for next year's car pays off, then we can be a lot closer and maybe it can be possible to win races."