Chelsea sacked manager Luiz Felipe Scolari on Monday after just seven months in charge of the Premier League club.
A poor run of form, culminating in Saturday's 0-0 draw at home to Hull City has left Chelsea all but out of the title race, seven points behind leaders Manchester United.
Scolari, who led Brazil to victory in the World Cup final in 2002 and led Portugal to the runners-up spot in Euro 2004, replaced Avram Grant as manager last year.
A statement on the club's website said: "Luiz Felipe Scolari has been dismissed as manager of Chelsea Football Club today (Monday) with immediate effect.
"The Chelsea board would like to place on record our gratitude for his time as manager.
"Felipe has brought many positives to the club since he joined and we all feel a sense of sadness that our relationship has ended so soon.
"Unfortunately the results and performances of the team appeared to be deteriorating at a key time in the season."
The statement said assistant coach Ray Wilkins would take charge on a temporary basis.
Scolari became the second Premier League manager sacked on Monday following the dismissal of Tony Adams from Portsmouth, but despite growing frustration from the club's fans towards him, his departure came as a surprise.
Chelsea are fourth in the Premier League and through to the knockout stages of the Champions League with an upcoming tie against Juventus, but Scolari has paid the price for what is now regarded at Stamford Bridge as an unsuccessful campaign.
The Brazilian started brightly at Chelsea with six wins and two draws from his first eight league games and they led the table most weeks until the middle of November.
However, Liverpool won 1-0 at Stamford Bridge on 26 October to end Chelsea's 86-match unbeaten home league run and their home form, in particular, began to dip alarmingly with another loss to Arsenal at the end of November and a series of poor draws.
The club slipped further back in the title race when they were beaten 3-0 by United and 2-0 by Liverpool recently. Saturday's draw with Hull proved to be one poor result too far.