Andre Villas Boas, who was relieved of his duties as head coach of London on Sunday, will be temporarily replaced by former assistant Roberto Di Matteo.
"Unfortunately, the results and the team's performance were not as expected, and positive developments were not visible," the official statement said.
The 34-year-old specialist began working with the English team last summer. "Chelsea" paid an impressive 15 million euros compensation for the specialist who had previously been in charge of "Porto."
Despite being one of the most promising European coaches, who won UEFA Europa League trophies, national championships, and the country's cup with "Porto," he failed to achieve good results in London: in the last 12 Premier League matches, the 'Blues' only managed to secure three victories and currently hold a modest fifth place.
In addition, "Chelsea" is on the brink of elimination in the Champions League round of sixteen: after a disappointing 1-3 defeat away to "Napoli" in the first leg, the Italians will be the favorites in London on March 14th. Furthermore, the team faces a crucial FA Cup battle away against "Birmingham" already on Tuesday.
Villas Boas' situation was not helped by persistent rumors of disagreements with senior players, especially with Frank Lampard. Rumors circulated that the young Portuguese was struggling to establish authority among the players, resulting in a less than ideal atmosphere in the dressing room.
Meanwhile, 41-year-old Di Matteo began his coaching career in 2008 when he took over at "Milton Keynes Dons" in the third division, and the following year received an offer to lead the "West Bromwich Albion" in the second division, earning promotion to the Premier League.
However, his time in the top division was not successful: after a crushing defeat against "Man City" in February 2011, he lost his job and later moved to "Chelsea," where he had been working as Villas Boas' assistant until now.