Williams chief technical officer Paddy Lowe is to take a "leave of absence" from Formula 1, the team confirmed to reporters on Wednesday.
Williams finished with only seven points last season, kept off the bottom of the constructors' championship only by the former Force India team, who were stripped of all points won before their takeover.
His departure comes after the team failed to complete its new FW42 chassis in time for it to participate in the start of testing.
After missing the opening two and half days' running in Barcelona, Williams deputy team principal Claire Williams said she was "embarrassed" that the team had failed to finish their 2019 auto on time but insisted a full debrief into the cause had not yet been carried out.
Two years ago, Paddy Lowe was the messiah for Williams.
Williams head to the season-opening Australian Grand Prix with the least amount of laps in testing.
Lowe is a director at Williams but it is unclear whether he has a shareholding in the company.
The FW42 was the second auto to be completed under Lowe's watch since he joined Williams from Mercedes two years ago.
That increased expectations for the FW42 but also raised the significance of the auto in terms of the competence of Williams's new senior structure.