Reports claim to have “heard only good ports things” about the potential transfer going through.
A new defender is high on the agenda for Manchester United boss Ole Gunnar Solskjaer ahead of the summer window.
Solskjaer is on the hunt for a partner for Victor Lindelof, who was the club’s only center-back to emerge from their car-crash campaign with any credit.
Koulibaly has established himself as one of the most highly-rated defenders in Europe after starring for Napoli.
The Senegal international has emerged as the Red Devils’ top target at the back.
It is expected Napoli will demand in excess of the £75m Liverpool spent to sign Virgil van Dijk from Southampton in January 2018.
But Goldstein understands that Old Trafford bosses will stump up the cash needed.
“The Koulibaly thing, I’ve heard only good things about the fact that him coming to United is very close,” Goldstein said on talkSPORT.
In other Man Utd news:
Napoli boss Carlo Ancelotti recently claimed Koulibaly is the best player in his position in the world.
“The best centre back in the world? I would say so,” Ancelotti said.
“And he can still improve. He is worth €150m and he is not available for transfer.
“Koulibaly’s contract expires in 2023, in 2021 there’s a €150m clause but Napoli do not need to sell, the president [Aurelio De Laurentiis] does not want to sell and the question doesn’t come up.”