The 31-year-old moved to Old Trafford from Chelsea in 2014, becoming a popular figure within the dressing room and the support base.
Mata’s current deal at United expires at the end of June but Press Association Sport understands negotiations over a new deal have gone positively.
The attack-minded midfielder has scored 45 goals in 218 appearances for United and a new contract will be a boost for a club in the midst of change.
Combative midfielder Ander Herrera and captain Antonio Valencia are leaving on free transfers, while there are questions marks over a number of other key players.
Paul Pogba is keen for a “new challenge” and Romelu Lukaku would welcome an Old Trafford exit, while question marks remain over the future of Alexis Sanchez and David De Gea.
Swansea’s Daniel James is the only summer arrival so far, while United are interested in Aaron Wan-Bissaka and Harry Maguire.
Belgium boss Roberto Martinez believes “it is clear” that Romelu Lukaku has to leave Manchester United this summer.
The 26-year-old endured a difficult second season at Old Trafford and has been linked with a move away.
The likes of Inter Milan have been reportedly showing an interest in Belgium’s all-time record goalscorer, who has netted 42 in 96 games since joining United from Everton in 2017.
However, he failed to find the back of the net in his last eight appearances of the season and was not an automatic starter under Ole Gunnar Solskjaer.
Now Lukaku’s international boss, who was also his manager at Goodison Park, feels everyone may benefit if the player secures a summer transfer.
“It is clear that he has to leave Manchester United,” Martinez told Belgian newspaper Het Laatste Nieuws.
“It would be a good thing for both parties. It is now important that Romelu finds the right club.”
Any potential departure for Lukaku could form part of an overhaul of Solskjaer’s squad.
The Red Devils finished the season poorly and ended the Premier League campaign in sixth place.
Paul Pogba’s future is also in doubt after the France midfielder suggested he is considering “a new challenge”.
United’s recruitment has so far been limited to the arrival of winger Daniel James from Swansea as a host of other big-names continue to be linked with the club.
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Pogba is taking time out to visit Korea and Japan as part of his sponsorship commitments.
In Tokyo on Sunday the 26-year-old midfielder indicated that a new “challenge” may be on the cards this summer. He then later admitted that he had been disappointed not to win any trophies with United, in pointed contrast to his World Cup-winning exploits with France in Russia a year ago.
“Obviously with my team (Manchester United) last season we arrived second (in Premier League), so we missed something,” said Pogba.
“I didn’t win any trophies with my team. But with the national team (France) it was obviously very good. Winning the World Cup made my season a good season, I would say personally, just because I won the World Cup.”