And that would hand Manchester United a boost in pursuit of their reported target.
Reports in Italy have previously linked United with a swap deal for Portuguese playmaker Mario – with Henrikh Mkhitaryan going the other way.
Corriere dello Sport claim Mario is being lined up as a January replacement after Mkhi was dropped from the squad for the Manchester derby.
He has also been linked with a £26million move to Arsenal.
Inter paid £40m to Sporting for Mario, 24, in 2016 and would look to recoup that fee.
Despite his huge price tag, the 31-cap Euro 2016 winner has seen himself relegated to the bench this season.
Paris Saint-Germain and Arsenal are also monitoring Mario’s situation as the highly-rated midfielder looks to kick-start his career elsewhere.
Inter sporting director Walter Sabatini said: “Joao has some issues with the lack of playing time.
“We don’t want to lose him. He is our player and we want to keep him.”