Former Chelsea boss Claudio Ranieri has revealed the Premier League Champions main problem this season.
The Nantes coach believes that Chelsea has been seriously hurt by the departure of Spanish striker Diego Costa.
Costa left Chelsea last month for a return to his former club Atletico Madrid after a break down in a relationship with Blues' manager Antonio Conte.
Costa will make his move official in January due to the transfer ban that prevented Atletico Madrid from signing any player until the next year.
Ranieri is of the opinion that Alvaro Morata is not a direct replacement for Costa. The Italian believes Morata still faces bedding in period.
He told Corriere dello Sport: “What has Chelsea's problem been so far? It's down to the injuries and the changes in the squad. It's not easy to go from Costa to Morata.
“The first is a leader, he carries the team on his shoulders and plays with anger, with force and sheer will. The other is more of a dribbler.
“When you change your centre-forward, you have to also change your approach."
Ranieri managed Chelsea between 2000 and 2004 after his sack he was hired by Valencia.
