Calcionapoli24 says United have now joined the list of clubs pursuing Napoli‘s Ruiz.
It was claimed Napoli president Aurelio De Laurentiis last summer rated the midfielder at £150million.
But it is understood they will demand closer to £76m for the 23-year-old Spaniard.
Ruiz has made 22 appearances this season, scoring once in the league.
He has impressed with his versatility to play in a deep or advanced central role, while even being deployed out wide on occasions.