Michael Emenalo has delivered a sucker punch to Chelsea by quitting his post as technical director.
Emenalo has walked away from the club after a 10-year association, where he has become one of Roman Abramovich's most trusted advisors.
The 52-year-old has overseen three Premier League title victories, as well as Champions League, Europa League, FA Cup and League Cup successes since joining the club.
But he has quit the Bridge, with a potential role at Monaco in a similar capacity set to be his destination.
"This has been a very difficult decision to make, but one I believe is right for both myself and my family, and the club," he said.
"I have had the privilege to work alongside some of the most talented people in the world of sport over the past 10 years, and I will depart incredibly proud of the achievements we have made. I wish Chelsea every success and look forward to following the club’s future triumphs from afar."
Emenalo was actively involved with Chelsea right up until Sunday's Premier League win over Manchester United, where he was seen on the touchline.
He was also present in Rome last week for the Champions League visit.
Emenalo is one of the few figures to have a long-standing role at Chelsea since Abramovich took over the club.
Antonio Conte added: "I am very sorry to see Michael leave Chelsea, and I would like to thank him for all his help and support since I arrived at this club. I have enjoyed working with him very much, we celebrated a Premier League title together in May, and I wish him the very best for the future."
The former Notts County player has worked with 10 different managerial regimes.
There have been rumours of discontent between Emenalo and current boss Antonio Conte following a frustrating summer in the transfer market.