Chelsea made a losing start to the Champions League for the first time as Basel came from behind to win 2-1 in Group E on Wednesday and deepen Jose Mourinho's difficulties during his Stamford Bridge homecoming.
Boos rang out at the final whistle after Marco Streller clinched Basel's first-ever win in England in the 82nd minute by flicking a header past goalkeeper Petr Cech after seizing on slack defending.
''I am responsible for everything,'' Mourinho said. ''Especially after a bad result. In the good moments I want everyone to shine, in the bad moments I want everyone to keep calm.''
Although Oscar lit up a drab start by curling Chelsea in front before half time, the 2012 European Cup winners and reigning Europa League champions missed a succession of chances to extend their lead after the break.
And Mohamed Salah began the Swiss side's comeback in the 71st by bending in an equalizer before Streller ensured that Chelsea's worst start to a season in the decade under Roman Abramovich's ownership was prolonged.
The loss came exactly six years after Mourinho's first Chelsea reign was ended by Abramovich following a drab Champions League draw against Rosenborg.
This was even more embarrassing for the west London club.
Not since October 2003, when Claudio Ranieri was in charge at the start of Abramovich's ownership, had Chelsea even lost a game in the group stage.
This setback comes with Chelsea already three points off the Premier League lead after four games, having opened with two wins, a draw and a loss to sit in sixth place.
''We still believe in each other,'' Mourinho said. ''We need to keep together, stick together and try against Fulham (on Saturday) to get the result to wake up the team for a smile.''
The shock win drew acclaim from Basel's famous fans.
''Fantastic evening for Basel supporters, wow!'' tennis great Roger Federer wrote on Twitter. ''I am so happy, thanks FC-Basel.''
Winning European football elite competition remains the obsession at Stamford Bridge despite the Champions League finally being won under former coach Roberto Di Matteo in 2012.
Against Basel, there was no Fernando Torres in the starting lineup or even on the bench, with Samuel Eto'o, recently signed from Russian club Anzhi Makhachkala.
The Cameroon striker, a four-time African player of the year and the world's best-paid star while at Anzhi, couldn't even muster a shot on goal.
Chelsea's breakthrough instead came from Oscar in the 45th minute, with David Luiz, who had concerned Mourinho with his sloppiness in defense, bringing the ball forward.
The Brazil center back fed Frank Lampard and Oscar connected with a throughball before striking low past goalkeeper Yann Sommer.
After an insipid first half - the type of performance fans jeered during Rafa Benitez's interim reign last year - Chelsea discovered some spark after the break.
But, first the cross bar denied Oscar and, when he tried to curl a shot into the net from a similar position outside of the area, the ball went wide.
The pressure was increasing, but a second goal proved elusive.
A towering header from Branislav Ivanovic was saved by Sommer at close range and the defender saw another header from a free kick nodded clear.
For all the incisive football, Chelsea was left reeling when Basel finally found its stride to stun the hosts.
Slick build-up play allowed Marco Strelle set up Salah to curl in the leveler from the edge of the area.
Then, Chelsea defenders left Streller in space to meet Kay Voser's corner at the near post and compound the early anxieties for Chelsea at the start of a season that promised so much with the morale-boosting return of Mourinho.
