Koulibaly joined Chelsea from Italian Serie A side Napoli in a £33million deal this summer.
Newsonline report that the Senegalese international appeared to be an excellent piece of business by Chelsea manager Thomas Tuchel after he scored on his Stamford Bridge debut in the Premier League 2-2 draw against Tottenham Hotspur.
But the 31-year-old put in a poor display the following week in a 3-0 defeat to Leeds United, being shown a red card after picking up two bookings and has faced criticism for his performance since returning from suspension.
However, Capello feels Koulibaly simply needs to adapt to the speed of the English top-flight league, having spent so long in the more slow-paced Serie A.
“I would like to talk about the difficulties of Koulibaly at Chelsea,” Capello told Sky Calcio Club.
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“In Naples, he was doing everything by himself. His problems now depend on the speed with which they play in England.
“It is the same pace used by Udinese to give Roma fits. It is something that must make us Italians reflect.”
