Chelsea have told Napoli that they have made their final offer for central defender Kalidou Koulibaly and are now actively pursuing alternatives in case the Italian club refuse to let him go.

That could open the door for Chelsea to make a £25million bid for Torino defender Nikola Maksimovic, who is also wanted by Napoli and last week went on strike to try to force through a transfer, but AC Milan have warned the Blues off a move for Alessio Romagnoli.

Koulibaly emerged as Chelsea head coach Antonio Conte’s first-choice defensive target over the past month, but the Blues have failed with a series of bids for the 25-year-old as Napoli have so far held firm.