Mundo Deportivo says United will bid for Ivan Rakitic in January.
The Croatia midfielder, 31, has lost his first team place this season to summer arrival Frenkie de Jong.
And there's an acceptance inside Rakitic's camp that he needs to move on during the winter market.
Along with Rakitic, United are also interested in Barca teammate Ousmane Dembele.
The France attacker is also struggling for minutes after Barca's summer swoop for Antoine Griezmann.