Chelsea have sacked Roberto Di Matteo just hours after their Champions League defeat to Juventus.
The club have reacted swiftly to the 3-0 loss in Turin which took their hopes of reaching the last 16 out of their hands, and put them at risk of becoming the first holders to fail to reach the subsequent knockout phase.
The Blues have also failed to win any of their last four Premier League games, a run which has seen them slip from top to four points behind leaders Manchester City.
A club statement read: "Chelsea Football Club has parted company this morning with manager Roberto Di Matteo.
"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."
The statement continued: "The club faces a difficult task ahead in qualifying for the knockout stages of the Champions League as well as maintaining a strong challenge for the top of the Premier League while competing in three other cup competitions. Our aim is to remain as competitive as possible and challenge strongly on all fronts.
"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 historic Champions 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 club will be making an announcement shortly regarding a new first team manager."
Di Matteo took charge of Chelsea in March after the club had sacked Andre Villas-Boas, initially on a temporary basis.
He rescued the club's ailing Champions League campaign and steered them against all odds to victory over Bayern Munich in the final on the German team's home ground, having already secured the FA Cup.
He was given a two-year contract in June, but not before there had been major speculation over whether Guardiola would take over.
The season started well domestically but they have fallen slightly off the pace in recent weeks. Di Matteo has become the first top-flight manager to leave his post this season.
Roberto Di Matteo factfile
1970: Born May 29 in Schaffhausen, Switzerland, to Italian parents.
1988: Starts career as a midfielder with Schaffhausen.
1991: Joins FC Zurich.
1992: Joins FC Aarau and wins the Swiss Super League in his only season at the club.
1993: Moves to Lazio in Serie A.
1994: November - Makes Italy debut as a substitute in a 2-1 defeat to Croatia in qualifying for Euro 96.
1996: Joins Chelsea, then managed by Ruud Gullit.
1997: April - Scores his first international goal in a World Cup qualifier against Poland which Italy won 3-0.
May 17 - Scores what was then the fastest ever goal in an FA Cup final, netting after 42 seconds against Middlesbrough as Chelsea go on to win 2-0.
1998: March 29 - Scores as Chelsea again beat Boro 2-0 to win the League Cup.
May 13 - Wins Cup Winners' Cup with 1-0 win over Stuttgart in the final.
2000: May 20 - Scores the only goal of the game against Aston Villa to win the FA Cup for a second time.
2002: February - Retires due to injury aged 31 after failing to recover from a broken leg he suffered 18 months earlier in a UEFA Cup tie with St Gallen.
2008: July - Appointed manager of MK Dons in League One.
2009: May - Misses out on promotion as the Dons lose their play-off semi-final on penalties to Scunthorpe.
June - Appointed manager of Championship side West Brom.
2010: May - Wins promotion to the Premier League as the Baggies finish second in the Championship.
2011: February - Sacked by West Brom.
June - Appointed assistant manager to Andre Villas-Boas at Chelsea.
2012: March - Named the Blues' interim coach after Villas-Boas was sacked.
May 5 - Wins the FA Cup as Chelsea beat Liverpool 2-1 in the final.
May 19 - Leads Chelsea to the greatest achievement in the club's history as they win the Champions League by beating Bayern Munich on penalties in Munich.
June 13 - Appointed Chelsea's permanent manager and first-team coach on a two-year contract.
Nov 21 - Chelsea announce they have parted company with Di Matteo, the night after a 3-0 Champions League defeat to Juventus makes their qualification out of the group stages unlikely.