Barcelona signed Coutinho from Liverpool in January last year for an initial €120m (£103m) fee, although the deal could rise to €160m (£142m) after add-ons.
But the 26-year-old has struggled to make an impact at Camp Nou and has already been linked with a move away.
Coutinho did not consider a move away from Barcelona in the January transfer window but according to Goal, the Brazilian has failed to convince Ernesto Valverde of his ability to secure a regular role in the team.
And the report claims that Barcas hierarchy are ready to take a huge loss on Coutinho as they are willing to negotiate offers in excess of €80m for the midfielder.
United have reportedly held talks with intermediaries over a potential deal for Coutinho in the summer, although the club are believed to be prioritising other positions.
Coutinho, meanwhile, admitted his future remains unclear and conceded that he has not been happy with his performances for Barcelona.
In the last few weeks, months even, Ive not been playing well but I still want to improve, Coutinho told Movistar+ last week.
I came to Barcelona to give my best. I live for the moment.
You never know what the future holds.