During the previous campaign, the Blues had finished second in the Premier League and reached the semi-finals of the Champions League under the management of Claudio Ranieri. Russian billionaire businessman Abramovich wanted trophies, though, and believed that Mourinho, who had guided Porto to Europe's top club competition, was the man to deliver the goods.
Key players such as Petr Cech, Paulo Ferreira, Ricardo Carvalho and Arjen Robben all arrived at Stamford Bridge in the days that followed Mourinho's appointment, but arguably the most important signing of the Portuguese coach's first stint in charge of the club was made 10 years ago today.
Didier Drogba's form in France with Marseille throughout the previous term had alerted a host of clubs, including Juventus. The Ivorian striker scored 32 goals in all competitions, including five in the Champions League and then a further six in the UEFA Cup following his side's exit from the former of those two tournaments.
Despite the scramble for his signature, it was Mourinho and Chelsea that won the race, with a fee of £24m - then a record for the West Londoners - being paid for the Ligue 1 Player of the Year.
Upon his arrival in the English capital, the 26-year-old said: "I am very happy to be here and am looking forward to playing for my new team. I want to do well with my national team and my club, so I will do my best to be better than I was last season at Marseille. It is a big chance for me to come here and work with the coach and to play for my new team."
Even though he'd suffer a stomach injury early on in his time with the club, Drogba's first two seasons saw him play a major role in the club's back-to-back Premier League title successes. He also scored the winning goal in extra time against Manchester United as Chelsea lifted the FA Cup in 2007 and he'd go on to score numerous crucial goals.
As the managers at the Bridge changed on a frequent basis, Drogba's importance to the team didn't alter. His goals and dedication to the cause made him a real cult hero among the club's supporters alongside the likes of John Terry, Frank Lampard and goalkeeper Cech.
While he scored 157 goals in total for Chelsea, it will be the two times that he found the back of the net inside the Allianz Arena in 2012 that he will forever be remembered. On what was to be his last outing for the club before departing for China, Drogba headed in Juan Mata's corner late on to force the Champions League final against Bayern Munich into extra time.
Then, it was his converted penalty in the shootout that saw Chelsea get their hands on the trophy for first time ever in their history.
To confirm his departure during the summer of 2012, Drogba told the club's official website: "I wanted to put an end the speculation and confirm that I am leaving Chelsea. It has been a very difficult decision for me to make and I am very proud of what we have achieved, but the time is right for a new challenge for me. As a team we have accomplished so much and have won every single trophy possible."
He would spend only a few months in the Far East with Shanghai Shenhua, before signing for Turkish side Galatasaray in January 2013. He's now left the Istanbul-based outfit and is a free agent. Rumour has it that his story with Chelsea may not have concluded just yet.