Williams chief technical officer Paddy Lowe is to take a leave of absence, the team confirmed to reporters on Wednesday.
The team missed the opening two and a half days of testing for the 2019 season due to the late completion of the car, with deputy team principal Claire Williams describing the delay as "embarrassing". Williams' 2018 car finished bottom of the championship -- the team's worst ever season -- although both Lowe and Claire Williams insisted throughout pre-season that his job was safe.
But a spokesperson for the team said that Rowe will be "taking a leave of absence from the business for personal reasons". The team did not say how the leave of absence would affect his long-term future.
The 2019 Formula One season is just over one week away with the opening race of the season taking place at the Australian Grand Prix on March 17.
The family-owned British team, who scored only seven points from 21 races last year, have an all-new lineup for 2019 with Formula Two champion George Russell and Poland's Robert Kubica.
Information from Reuters contributed to this report