Chelsea part company with manager Roberto Di Matteo.
The announcement follows Chelsea's 3-0 defeat to Juventus on Tuesday which left them on the brink of elimination from the Champions League.
"The team's recent performances and results have not been good enough and the owner and the Board felt that a change was necessary now to keep the club moving in the right direction as we head into a vitally important part of the season," Chelsea said on their website.
"The club faces a difficult task ahead in qualifying for the knockout stages of theUEFA Champions League as well as maintaining a strong challenge for the top of the Premier League while competing in three other cup competitions."
"The owner and the Board would like to thank Roberto for all he has done for the club since taking over in March. Roberto helped guide us to an historicChampions League victory and a seventh FA Cup.
"We will never forget the huge contribution he has made to this club's history and he will always be welcome at Stamford Bridge," the statement said.
Chelsea made a flying start to the season under Di Matteo, winning seven and drawing one of their opening eight Premier League games to go four points clear at the top of the table.
Since then, however, they have won just two of their last eight games in all competitions, slipped to third in the league and are on the brink of suffering the ignominy of becoming first holders to go out of the Champions League at the group stage.