Williams is determined to put an end to its recent decline in performance, with deputy team principal Claire Williams saying her team must improve on last year's championship position.
After finishing third in 2014 and 2015, Williams slipped to fifth in 2016 and 2017 as Force India replaced it as the best of the rest behind F1's big three teams Mercedes, Ferrari and Red Bull. With McLaren and Renault expected to make big steps in 2018, Williams faces even more opposition this year, especially as it enters the season with the least experienced driver line-up on the grid.
"I think it's going to be incredibly challenging this year," Williams told ESPN at the launch event for the new FW41. "McLaren has its new engine and Renault has invested heavily within the infrastructure in its team, I think there's going to be a lot more competition out there, unfortunately, this year.
"But then it's our responsibility that they don't overtake us in the championship, and equally we've got Force India who are a fantastic team and absolutely deserve their P4 last year.
"For us it's about what we need to change and we are a big team and have been in the sport for more than 40 years now and we have the infrastructure, we have the people, we have 700 people working on our racing team and we should be able to deliver a competitive race car. That's really what we have to be aiming for.
"I'm not going to set any targets, I think it's dangerous to do so, but we can't finish P5 or lower this year."
Williams also defended her new driver line-up of Lance Stroll and Sergey Sirotkin, which is the youngest and least experienced pairing on the grid.
"For us there has been a huge amount of negativity out there, which I don't quite understand. Why do people judge before they have seen the talent on the track? Let's see how they do, let's give them the opportunity to see how good they can be, and then we will have the conversation about it."