Michael Emenalo has decided to step down as Chelsea technical director after a decade at the club.
Chelsea confirmed the surprise news on Monday just a day after Chelsea beat Manchester United at Stamford Bridge, a game Emenalo watched on from the bench, and brings the 52-year-old's long association with the club to an end.
Emenalo - who heads player recruitment and oversees the club's academy and youth networks - is one of Chelsea owner Roman Abramovich's most trusted advisors.
During his time at Stamford Bridge, the club have won three Premier League titles, the FA Cup, the Champions League, the Europa League and the League Cup.
It is unclear what Emenalo, who handed in his resignation this week, will do next but he admitted the decision to leave had been a hard one.
Speaking to Chelsea's official website, 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."
The club are expected to review their management structure following Emenalo's resignation.
Emenalo's decision to quit comes after coach Antonio Conte's position at the club came under scrutiny in recent weeks.
In Pictures | Chelsea vs Manchester United | 05/11/2017
The Italian, who was appointed as Chelsea manager in 2016, has regularly expressed his frustration at the club's recruitment policy this summer, led by chief executive Marina Granovskaia and Emenalo, which went on to precede an inconsistent start to the season.
Conte made the shock decision to leave regular centre-back, and an Abramovich favourite, David Luiz out of his squad for the visit of United on Sunday, with the Chelsea boss insisting the decision was down to "tactical" reasons.
Read More
Cutting an animated figure behind Conte at Stamford Bridge, Emenalo joined Luiz and Kenedy on the bench to watch Chelsea beat Jose Mourinho's side 1-0.
Conte, however, is believed to have had a good relationship with Emenalo, and said he was "sorry" to see him go.
The Italian 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. 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."
Emenalo originally joined Chelsea in October 2007 alongside Avram Grant and, under Carlo Ancelotti, he was tasked with the aim of heading up opposition scouting and acting as a first-team coach.
He was promoted to the role of technical director in July 2011 and, despite largely remaining in the background, the former Nigerian international took centre stage when Jose Mourinho was sacked in 2015.
Emenalo gave an in-house interview with Chelsea TV where he blamed "palpable discord" between Mourinho and his players for Chelsea's disastrous start to the 2015-16 season.
His rise in the football world began with Emenalo, a defender, playing in Belgium, Germany, England - with Notts County - America, Spain and then finally Israel where he met Grant.
MORE ABOUT