Neither Valtteri Bottas nor Felipe Massa was a top ten threat throughout the weekend in Monte Carlo, with both men missing Q3 for the first time this year and then finishing Sunday's race in 14th and 15th respectively.
"We know we still have a good car and go to races in the next few weeks where we should be able to demonstrate our true performance," said Bottas, predicting a return to the sharp end of the grid in Montreal.
"This has been a tough weekend that ended in an even tougher race. We tried everything to try and get some points but with the pace we had it wasn’t possible today. There are not too many positives from the weekend but plenty we can learn from as to why we struggled."
Massa added: "The car has not had its usual performance all weekend but we know that we are heading to tracks in Canada and Austria that suit our car and we should be back fighting towards the front.”
Rob Smedley, head of vehicle performance at Williams, said a lowly performance on Saturday had hurt the team most, but stressed that they will now regroup ahead of racing in Montreal.
"It was quite a difficult weekend and we were nowhere near where we should be," he said. "At Monaco, if qualifying doesn’t go well you have partly made your bed so we knew getting points was going to be tough.
"We have to look at all areas to see what went wrong here with the inherent car performance and set-up. We cannot return here in 2016 and repeat this performance.
"We now have to focus firmly on the next three races. We have a really good package and some healthy upgrades coming soon so we look forward to coming back stronger in Canada.”
Monaco was the first race this year in which Williams have failed to score points. It was also one of their worst Grands Prix last year - they scored just six points, their equal-lowest of the entire season. They currently sit third in the 2015 constructors' standings, 29 points ahead of Red Bull.