Williams chief technical officer Paddy Lowe has admitted that the team has made some serious mistakes in the development of this year's FW41.
"The pace is really quite bad," he told reporters this week in Barcelona. "The car isn’t good enough, it’s not what it should be.
"There are some issues with it, which fortunately we think we understand," he added. "There is something that is really disrupting the drivers’ ability to drive the car anywhere near the limit."
Williams missed out on the points in the Spanish Grand Prix. And the team continued to struggle during two days of in-season testing at the Circuit de Barcelona-Catalunya during the week.
"We’re very busy doing a lot of work to fix those issues," he said. “None of those fixes are in place [at the moment] unfortunately.
"We haven’t yet brought anything that solves those," he continued. "That's why we were struggling so much at a circuit which is an unforgiving track for underlying car performance.
"We shouldn’t expect it to be any better. But we will do in due course."
Lowe insisted that the car had its plus points too, and said that the team was far from giving up on 2018.
“We are not writing off this season. From the minute this car ran, it was clear there were some issues we had to deal with," he said.
"There are many things that are good about the car and they are unable to show themselves, because the car is let down particular aspects."
The team's long-time chief designer Ed Wood left the team earlier this month but Lowe was quick to say that Williams' current struggles were not down to Wood. Instead, he preferred to take the hit himself.
“We have to accept we haven’t done a good job,” Lowe acknowledged. "We just lost our way in some critical areas, which we now understand.
“I haven’t done a good enough job in making the right level of progress. I’ve been with the team 12 months, and there are things which we should have responded to earlier."
Among the changes that have been made in recent months have been the hiring of Ferrari's Dirk de Beer as head of aerodynamics, and McLaren's Doug McKiernan coming on board as chief engineer.
Lowe said that the personnel changes were all part of a bigger plan of get Williams back on its feet.
“We have put in place a programme with the team, which we call a recovery programme," he said.
He explained that the idea was to "bring back the car back to the level we intended to operate" but admitted that it was still early days and a work in progress.
"That programme is timed up to the midseason point. I can’t guarantee anything."