Michael Emenalo has resigned from his role as Chelsea technical director, the Premier League club have announced.
Former Nigeria international Emenalo has been a key confidant of owner Roman Abramovich, acting as a link between the first team and the Blues board.
The former Notts County defender joined Chelsea in October 2007 and has been technical director since July 2011. He has already been linked with a position at Monaco.
Chelsea said in a statement: "Chelsea Football Club today announces that technical director Michael Emenalo has decided to stand down from his role."
Chelsea said Emenalo had "contributed to a period of unprecedented success for the first team and academy".
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 wish Chelsea every success and look forward to following the club's future triumphs from afar."
Head coach 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.
"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."
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There were many serious allegations made against Mr Abramovich by Mr Berezovsky, including attacks on Mr Abramovich's honesty and integrity.
We are pleased that the judge has firmly rejected all such allegations and has described Mr Abramovich as a truthful and frank witness who showed a responsible and honest approach when giving evidence in this case. We appreciate that, to many people, this case has been a uniquely Russian one, and should therefore have been heard in the Russian court system.
Nevertheless, Mr Abramovich has always had great faith in the fairness of the English legal system and is both pleased and grateful for today's outcome.
He stated from the outset that there was no merit to the allegations made by Mr Berezovsky, and this position has now been comprehensively vindicated by the court.
Boris Berezovsky said he had "no regrets" about taking his case against Roman Abramovich to court.
He said he did "not understand what happened" in court today and that he "needs to analyse on what happened".
Boris Berezovsky said he was "absolutely amazed" and "surprised completely" by today's ruling, outside the High Court.
He added that Mrs Justice Gloster tried to "re-write Russian history".
Boris Berezovsky looked impassive when the judge went through her reasons.
The judge described Berezovsky as an "unimpressive" and "unreliable" witness who at times clearly made up his evidence.
Abramovich on the other hand was "truthful" and on the whole a "reliable" witness.
Mrs Justice Gloster announced in a summary of her judgment:
On my analysis of the entirety of the evidence, I found Mr Berezovsky an unimpressive, and inherently unreliable, witness, who regarded truth as a transitory, flexible concept, which could be moulded to suit his current purposes.
At times the evidence which he gave was deliberately dishonest; sometimes he was clearly making his evidence up as he went along in response to the perceived difficulty in answering the questions in a manner consistent with his case; at other times, I gained the impression that he was not necessarily being deliberately dishonest, but had deluded himself into believing his own version of events.
On occasions he tried to avoid answering questions by making long and irrelevant speeches, or by professing to have forgotten facts which he had been happy to record in his pleadings or witness statements.
He embroidered and supplemented statements in his witness statements, or directly contradicted them.
When announcing that Russian oligarch Boris Berezovsky had lost his High Court battle,Mrs Justice Gloster said she found Mr Abramovich "to be a truthful, and on the whole reliable, witness".