But with Kurt Zouma hoping to return from injury by the end of the year it will undoubtedly increase the competition in defence for Cahill and also for 35-year-old Terry who signed a 12-month contract extension after being urged to do so by the new manager.

And neither is Koulibaly expected to be Chelsea’s final big signing of the summer window with the club still in the market for another striker and a growing sense that they will, finally, test Everton’s resolve to hold onto Romelu Lukaku before the window closes.

Everton are yet to receive an official Chelsea bid for Lukaku, who would also cost upwards of £60 million, but it is known that the London club would like to bring their former striker back. Chelsea will keep Diego Costa, with Atletico Madrid having given up on re-signing him after they bought Kevin Gameiro from Sevilla, but want another striker despite having spent £33 million on another Belgian, Michy Batshuayi.