Antonio Conte has endured a relatively quiet summer so far since taking charge at Stamford Bridge, with Michy Batshuayi and N’Golo Kante the only additions to his squad.
Although both cost a combined fee of around £65m, there is thought to be money to spend in west London, with the Italian gaffer trusted with £140m.
And reports claim that £60m of this may be sent to Napoli for Koulibaly.
The Senegalese defender, who stands at 6ft. 5”, has already been the subject of a bid of around £38m from Chelsea, but the club are seemingly eager to pay much larger fee to secure his signing.
The potential addition of the 25-year-old will plunge John Terry’s long-term future into doubt, with the veteran skipper’s contract due to expire at the end of the current campaign.