Nantes coach Claudio Ranieri believes Chelsea have been hurt by the departure of Diego Costa.

The Spain striker left Chelsea last month to return to Atletico Madrid after a chaotic summer.

While he cannot formally sign for Atletico until January, Costa is training with his new club and will not play for Chelsea again after the two sides agreed a transfer worth up to £57.2million.

Former Blues boss Ranieri, meanwhile, has cast doubt on Alvaro Morata as a readymade replacement. The Italian believes Morata still faces a 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 Diego 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 the Blues between 2000 and 2004.