According to Corriere dello Sport (h/t Jack Otway of the Daily Express), the Red Devils have switched their attention from Inter winger Ivan Perisic and will instead pursue a deal for the Portuguese playmaker.
It's reported the Red Devils are keen to bolster their midfield options, with Marouane Fellaini's contract set to run out at the end of the season. Even so, they are ready to offer Mata as part of a package for Mario.
The Inter man has failed to show his best form since joining the club last summer. While Inter are top of the Serie A table this term, he's only started four games in the top flight.
WhoScored.com's Cristiano Acconci believes the former Sporting CP man has a lot to offer at the San Siro, but he needs to improve his application:
Mario showcased plenty of ability during his stint in Lisbon to suggest he could become one of the most effective creative midfielders in Europe.
Whether utilised on either flank, as a No. 10 or occasionally in a deeper role, Mario always looks to be positive in possession. His control in tight areas, dribbling skill and passing ability makes him so difficult to pin down. If the Milan side can find a way of getting him into the current setup more regularly, he'd potentially push them to another level.
As noted by Portuguese football journalist Marino Peixoto, he played well in the 5-0 win over Chievo on Sunday:
Marino Peixoto @Marinovpeixoto
João Mário vs Chievo Verona: - 108 touches - 83/90 passes completed - 3 key passes - 2 shots on target - 0/0 dribbles completed - 7.8 rating from @WhoScored By no means his best performance but a composed one. Fantastic to see him play a full 90 again. https://t.co/dNWNbxyJLW
Interest from United would be understandable, although if the club were to put Mata up as part of any deal it would split opinions.
The Spain international may not be the first name on Jose Mourinho's teamsheet, but he's become one of the most popular members of the United side since arriving at Old Trafford in 2014. Additionally, his technique, creativity and penchant for chipping in with crucial goals has made him a valuable asset.
The 29-year-old hasn't found top gear this season, although whenever he is on the pitch there are moments of class that shine through, as noted by Agence France-Presse's Tom Williams:
At the moment, the players trading places would be a fascinating concept. Arguably, the more combative style of Mario would be a better fit for the Premier League, whereas Mata's guile and flair would make him a big hit in Serie A, where the slower pace of the game would allow him to have a bigger influence.
Still, swap deals are rare in the modern game, and if deals were to be done for either player, you sense they'd be independent of one another. At moment, both players will surely feels as though they still have something to offer their respective sides over the course of a long campaign.