One of the key confidants of Chelsea owner Roman Abramovich quit the English champion for family reasons on Monday.
Michael Emenalo spent 10 years at Chelsea, joining as a scout before becoming the assistant coach of the first team and more recently the club technical director.
The former Nigeria international acted as a link between the squad and Chelsea's board, and had an influence on transfers and developing players from the academy.
After much deliberation, Emenalo chose to leave to spend more time with his three young boys.
Some of the most important figures at the club, including manager Antonio Conte and chairman Bruce Buck, said they were sad to see Emenalo depart.
Director Marina Granovskaia said Emenalo "played an important role during the most successful period in the club's history, helping make Chelsea the club it is today."
Chelsea said the club will be reviewing its management structure, with the help of Emenalo.