Koulibaly could become available for just £69million, says Il Mattino.
The 28-year-old is said to be one of the Napoli stars who have hired bodyguards to protect themselves and their families from ultra fans following their abysmal start to the season.
Napoli are ready to part with Koulibaly for a cut-price figure of just £69m.
That could be music to United's ears after they failed to sign him in the summer with a much higher offer.
Napoli president Aurelio De Laurentiis revealed last month: "I loved Koulibaly the man so I refused the £91m offer, but a time will come when I'll have to sell him."