The easy option for Kalidou Koulibaly last summer was to stay with Napoli. He was a club legend, viewed as one of Serie A's standout central defenders, and his family was firmly settled after eight years in the vibrant Italian city. Yet the lure of playing Premier League football – and for Chelsea – proved too much.
A deal worth £33.8million was swiftly concluded and Koulibaly joined his new teammates during their tour of the United States. The hope on the part of Chelsea, and then-head coach Thomas Tuchel, was the Senegal international would prove a worthy replacement for Antonio Rudiger.
Koulibaly knew that would not be easy. After almost a decade in Italy, an inevitable period of adaptation would be required. Mistakes would be made along the way. "I will have to adapt everything because the speed is faster in the Premier League," the 31-year-old said at his unveiling press conference.
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"I have to think faster in my head, go faster, and move my eyes faster. This is more difficult for players in the Premier League. In Serie A, everything is more with the brain, calmer. You have to think of every movement. Here, you have to think very fast, and this is the first thing I have to change.
"The most important thing is to have good behaviour to understand everything really fast. I will need time for sure because I can't be the player everyone wants from the first game. I will take my time – and I hope in two or three months – I will be the one everyone is waiting for."
Koulibaly's debut ended with Chelsea keeping a clean sheet and winning away at Everton. His first outing at Stamford Bridge came against Tottenham; the centre-back scored a stunning volley in what ended as a 2-2 draw. But then came the difficulties Koulibaly predicted.
He was sent off for two clumsy challenges against Leeds and amassed five yellow cards in his next 11 appearances prior to the World Cup break. Within the frenetic world of the Premier League, Koulibaly appeared cumbersome and lethargic. In the Champions League, he looked more at ease.
It was in mid-January that Graham Potter opted to take Koulibaly out of his starting XI – and Chelsea subsequently kept three consecutive clean sheets. Koulibaly returned for the dismal defeat to Southampton and was fortunate not to be sent off before being replaced at half-time. He then played 90 minutes as the Blues were beaten by Tottenham.
Koulibaly needed a circuit breaker. It came in the form of an injury to Thiago Silva and Graham Potter's decision to revert to a 3-4-2-1 formation. It resulted in the former Napoli captain being deployed in the middle of a back three and he impressed in outings against Leeds United, Borussia Dortmund, and Leicester City.
The position gives Koulibaly extra security; he is no longer being dragged into wide areas and left exposed in one-vs-one situations against skilful attackers. That defensive work is left to the more mobile and quicker Wesley Fofana and in the previous two matches, the terrier-like presence of Marc Cucurella.
Koulibaly remains active in his defending but his approach as the middle centre-back is measured. He has, in this respect, assumed the Silva role: an experienced head who marshals the backline rather than trying to dominate opponents.
"I’m a guy who works a lot," Koulibaly told Chelsea's in-house media last week. "I like to work, I want to always improve. I know some people were waiting for more from me, but I’m easy. I just keep on going, keep on getting to know my team, every player, and everybody at the club, because the club is really important.
"When you have all the confidence of everybody, then you can show your quality on the pitch. I want to show I am a player of Chelsea and I want to give everyone a lot of happiness."
The Koulibaly redemption arc is not complete – and it's difficult to envisage the Senegalese keeping his place in the defence when Silva returns from injury. However, Koulibaly appears to have finally settled at Chelsea, even if it has taken longer than he even anticipated.
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