Felipe Massa has claimed that Williams are still behind Ferrari in terms of team organisation, despite ending 2014 ahead of the Italian outfit.
The Oxfordshire-based team had finished 2013 in ninth in the constructors' championship, but completed a remarkable turnaround last season to beat the Scuderia to third place in the standings.
However, Massa claims that there are still areas for improvement at Williams in terms of organisation.
He told Autosport: "In my opinion, the biggest difference, on a negative point, is that Williams's organisation is less complete. In Ferrari it wasn't complete, but was perhaps more organised as a big team.
"Williams is like a new team with so many new people and they are doing many different things this year than they were before and it's also a change of mentality.
"I think the good thing is that Williams is working so well in the windtunnel. The car improved the most from the first to the last race during the season - their rate of improvement was probably more than any other team."
Massa finished seventh in the drivers' standings.
