Chelsea technical director Michael Emenalo has stepped down from his post after 10 years with the club.
The 52-year-old, who played for Nigeria at the 1994 World Cup, joined Chelsea in 2007 under Avram Grant, for whom he played at Maccabi Tel Aviv.
He worked in both scouting and coaching departments at Chelsea before being promoted to technical director in 2011.
Emenalo, who played for Notts County in the 1990s and in the first MLS game, has been linked with a role at Monaco.
During his time at Stamford Bridge, Chelsea won the Champions League in 2012, plus three Premier League titles, three FA Cups, the League Cup and Europa League.
Emenalo said: "This has been a very difficult decision to make, but one I believe is right for both myself and my family, and the club.
"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."
Chelsea boss Antonio Conte said: "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."
Chelsea chairman Bruce Buck said: "It is with regret that the owner and board of directors accepted Michael's resignation this week. We are sorry to see him go but understand his desire to move on and explore new challenges."
BBC Sport's Simon Stone
Whilst the turnover of managers under Roman Abramovich has been large, for 10 years Emenalo's presence has been a constant.
Whether he exerted it to the levels it has often been suggested, there is no doubt Emenalo had influence at Stamford Bridge.
Abramovich trusted him and losing the Nigerian will be a significant blow as it robs the Chelsea owner of his link to the playing side.
It is also a surprise because Emenalo has been passionate about Chelsea's progress.
Despite the criticism it had endured, he believes in Chelsea's youth policy and feels, in Andreas Christensen, Tammy Abraham and Ruben Loftus-Cheek, the club are developing players who can emulate John Terry in reaching the highest level.
Emenalo's exit could be viewed as a victory for manager Antonio Conte, who may feel he can now impose more of his own ideas on the club.
However, it is only when the results of an internal review of Chelsea's management structure that Emenalo will have an input into are known that the true impact of today's announcement will be felt.