Rafael Benitez has revealed that Kalidou Koulibaly must improve his concentration if he is to succeed in the Premier League after the 31-year-old made the switch to Chelsea.
The Blues confirmed that the Senegal international has joined the club from Napoli for a fee in the region of £34m on Saturday morning, becoming their second signing of the transfer window. This is after Raheem Sterling made the big-money move from Manchester City earlier in the week.
Koulibaly is an experienced centre-back, who made more than 300 appearances for Napoli during his eight-year spell in Italy. He has been named in the Serie A Team of the Year on four separate occasions and also lifted the Africa Cup of Nations with Senegal back in February after they beat Egypt in the final.
