The Portuguese tactician was one of the best things to happen to Chelsea. Soon after Abramovich bought the club Mourinho was brought in as manager replacing Claudio Ranieri. He utilized the money intelligently and brought in players who would fit his style of gameplan.
The "Special One" got his equations correct and Chelsea won two consecutive Premier Leagues, two League Cups, an FA Cup, and a Community Shield. Under his spell Chelsea transformed from an average club to a powerhouse of European football.
However, the Special Era did not last long as differences between him and Abramovich started to mount regarding the signing of Shevchenko much against the Portuguese's wishes.
Abramovich's insistence on Mourinho playing the Ukrainian was widely seen as reason of further friction in relations between the two men. On 20 September 2007 Mourinho left Chelsea "by mutual consent."
After Mourinho left Chelsea saw a dip in their form. The next season was highly unsuccessful under Scolari, who was eventually sacked halfway through. Hiddink took responsibility as caretaker manager for the rest of the season. Chelsea presently has been performing well under new manager Ancelotti.
Mourinho's departure was shocking and sudden. After his departure Chelsea has not seen much success. Unless Chelsea wins the league or an European honor the gap left by the "Special One" will not be filled.