London - Real Madrid boss Jose Mourinho believes that his former club Chelsea could struggle this season without striker Didier Drogba.
Mourinho signed Drogba when he was Chelsea manager but the Ivorian left Stamford Bridge in the summer after an eight-year stay which saw him win three Premier League titles, four FA Cups, two League Cups and the Champions League.
The 34-year-old sealed the European success over Bayern Munich in May with the winning penalty, having already scored in normal time - his 157th and final goal for the club - and has since moved to Chinese club Shanghai Shenhua.
Chelsea's Champions League defence began with a 2-2 draw at home to Juventus on Tuesday and Mourinho believes it is only a matter of time before the Londoners start to miss Drogba.
"I believe Drogba is the big difference for them," Mourinho told Sky Sports News.
"I don't think you can replace him. You can buy top players and invest like Chelsea did, but there is only one Drogba, in the Premiership and Chelsea's history.
"Drogba means crucial moments. The final, a top match, Drogba is there. When the team is losing at home, Drogba is there. Chelsea will miss Drogba and Drogba will mean a few less points. But the team is good, with good players and they are European champions."
Mourinho kickstarted the Chelsea's run of success by guiding them to back-to-back titles in 2005 and 2006.
And, although he has reiterated his love of the club, he says he will be returning to England and to any club when his time with Real comes to an end.
"I cannot deny what is clear in my mind. After Real Madrid, England, that's for sure. I keep saying the same, I know clearly," he added. "In England (I could manage) everyone. I am blue, but I am London blue. I am a professional."