The 24-year-old has been heavily linked with a move to Old Trafford in recent weeks, with English publication 'the Daily Mail' reporting that the 'Red Devils' tried to push through a £40m move for the playmaker back in 2016, only for him to plump for a switch to Inter.
However, Mario's time in Italy hasn't exactly gone to plan so far, with the player failing to secure a regular place in the 'nerazzuri' first team.
The midfielder, who impressed with a series of dominating performances in the middle of the park during Portugal's Euro 2016 triumph, has made just 11 appearances in all competitions so far this season, a total that he is far from happy with.
Speaking to 'Sky Italia', Inter's sporting director Walter Sabatini has admitted that the Portuguese has expressed his concerns to the club, but insisted that Inter's intention is to keep the player.
'Joao has some issues with the lack of playing time,' Sabatini explained.
'We don't want to lose him. He is our player and we want to keep him.'
United manager Jose Mourinho knows all about Mario's ability and reports in Italy claim that he could be about to renew his interest in the midfielder, with Henrikh Mkhitaryan potentially set to be used as a makeweight in a deal.