Jose Mourinho's tumultuous second spell as Chelsea manager was ended "by mutual consent" on Thursday, with the club's technical director revealing that squad disharmony was a significant factor.
Chelsea's disastrous start to the season prompted owner Roman Abramovich to press the ejector button, with the club saying it was "in the best interests of both parties to go our separate ways".
Nine defeats in 16 games have seen the reigning Premier League champions slither to within a point of the relegation zone and technical director Michael Emenalo said that Chelsea had had no choice but to act.
"Whilst there is huge sentiment for the individual who has done so much for the club, the facts of the matter remain that Chelsea Football Club is in trouble," he told Chelsea TV.
"The results are not good. There obviously seems to be a palpable discord between manager and players. We feel it was time to act."
Chelsea said that Mourinho, 52, had left "on good terms", two years after returning to the club following spells at Inter Milan and Real Madrid.
He was pictured on Sky Sports News being driven out of Chelsea's training ground in a black car, with his hood pulled down over his face.
The outspoken Portuguese is reported to have been informed of his fate in a meeting with club officials on Thursday afternoon, following two days of talks at boardroom level.
"His three league titles, FA Cup, Community Shield and three League Cup wins over two spells make him the most successful manager in our 110-year history," Chelsea said in a statement.
"But both Jose and the board agreed results have not been good enough this season and believe it is in the best interests of both parties to go our separate ways." Chelsea said that Mourinho "will always remain a much-loved, respected and significant figure at Chelsea" and "will always be warmly welcomed back to Stamford Bridge".
He was previously sacked by Abramovich in 2007 and his departure on Thursday came just seven months after he led Chelsea to a league and League Cup double.
Dutch coach Guus Hiddink, 69, has been cited as the front-runner to take over on a short-term basis, having previously fulfilled the role in 2009.
Atletico Madrid's Diego Simeone and Italy coach Antonio Conte are reported to be possible long-term successors, along with longstanding target Pep Guardiola, the Bayern Munich coach, and ex-Chelsea manager Carlo Ancelotti.
"The club is working vigorously and actively to make sure that the situation with regards to a managerial appointment is taken care of as soon as possible," Emenalo said.
Chelsea have cancelled Friday's scheduled press conference, when Mourinho had been due to address the media ahead of Saturday's home game with Sunderland.
In his final interview as Chelsea manager, filmed for BT Sport before his departure was announced, Mourinho said the team's travails had been a useful experience.
"As a process, this is an amazing learning process," he said. "This period was important for me. I'm better than I thought." In what proved to be his last game, Chelsea were beaten 2-1 at Leicester City on Monday - a club managed by Claudio Ranieri, who he replaced at Stamford Bridge when he first arrived from Porto in 2004.
Mourinho lambasted his players afterwards, saying: "I feel like my work was betrayed." Emenalo's comments confirmed reports of dissent within the squad.
Mourinho also said that Chelsea could no longer achieve the top-four finish necessary to qualify for next season's Champions League. They currently trail fourth-place Manchester United by 14 points.
Cesc Fabregas was the first Chelsea player to pay tribute to Mourinho, tweeting: "Thank you for all you have done for me. I owe you a lot and we will all miss you.
"Good luck in the future and I know you will be back soon." With Chelsea having swept to the title by eight points last season, their collapse has baffled pundits.
As well as floundering in the league, they were knocked out of the League Cup on penalties by Stoke City, although they have reached the Champions League last 16, where they will face Paris Saint-Germain.
Things went awry from the off, with Chelsea losing to Arsenal in the Community Shield and then drawing 2-2 at home to Swansea City on the season's opening day.
That game was overshadowed by Mourinho's criticism of his medical staff for running on to treat Eden Hazard, which temporarily left his team down to nine men.
Team doctor Eva Carneiro left the club in September and is now seeking a claim for constructive dismissal.
Chelsea then lost 3-0 at Manchester City and have also lost to Crystal Palace, Everton, Southampton, West Ham United, Liverpool, Stoke and promoted side Bournemouth.