Antonio Valencia confirmed the news in an Instagram post congratulating his return, as Mata arrived at The Lowry Hotel with the rest of the team on Saturday.
Reserves midfielder Scott McTominay has also been promoted to the first team in the absence of the suspended Marouane Fellaini and injured Timothy Fosu-Mensah, reports the Manchester Evening News.
The 29-year-old underwent groin surgery just over four weeks ago and United manager Jose Mourinho said he was scheduled to return ‘at the end of May’.
However, the Spain international hinted at a return before the end of the season in his Monday blog and could make the teamsheet versus relegation threatened Swansea.
“I think the first one to come back is Mata,” Mourinho said on Thursday. “Which will give us another option in attack, but in reality what we need now is one of the two centre-backs to be back.”
Daley Blind, who lives in the city centre, tends to rendezvous with teammates at the hotel.
“Yes, he’s an option,” Mourinho said of Wayne Rooney playing in midfield. “We don’t have [any other players there]. We have Herrera and Carrick and nothing else.
“And Tim Fosu-Mensah, like today, an emergency to help the team, strong legs, energy, he’s another one that we will miss, so we are in trouble but we will fight, that’s for sure.”
Mourinho spoke of how happier the United squad was following predecessor Louis van Gaal’s departure.
“The group was a nice group, honestly, the group was a nice group,” Mourinho added. “Good people good boys, committed people, so I think Mr Van Gaal left here a good group of boys with very good relations between them, and that I got in my hands.
“I think they missed happiness, they missed trust, they missed belief, they missed this extra bit that brings resilience, brings you fight, and they have it.
“So the group, next July 9, when we meet again for next season, is a strong group, so the new players, when they will arrive, will find a group more ready to go for big things.
“But the reality is that we are fighting to win the Europa League and we are fighting to try to finish fourth, so let’s go.”
Mourinho remains reluctant to giving Axel Tuanzebe his full debut despite United’s limited options in central defence.
“In this moment he [Bailly] is the only option we have,” Mourinho stressed. “It’s Axel, Eric and Daley. I think Eric and Daley they played again absolutely amazingly. I have to speak with them and see how they are, see how they feel.
“I’m also training hard in the gym so I can also be an option. Mourinho and Tuanzebe against Swansea.”
Mourinho was asked whether he regretted letting Morgan Schneiderlin and Bastian Schweinsteiger leave,
“Our decision. our decision,” he stressed of their departures. “To have lots of players without player is something that the players don’t want.
“We didn’t tell Morgan we want to sell you, Morgan asked and said ‘please sell me, I want to go and play every game’, so sometimes there is always this dilemma of keep a bigger squad, but then the players don’t want to stay. Even the younger players, when they are not playing, they ask to leave, so it’s very hard.
“We arrive in an extreme situation where, I think it must be unique in football, where we have two cruciate ligaments in the same match. In my career I had one in 17 years. One cruciate in 17 years. And now, against Anderlecht, I have two. In one match.
“We are very unlucky is the only thing we can say, and the other small injuries, the Pogba one, Valencia last week, are the injuries of fatigue, the accumulation of matches, which is normal. Smalling and Jones were with the English national team, training.
“So maybe it’s a blessing, an opportunity to make the team stronger, maybe it’s an opp to make them mentally stronger. Maybe it’s a blessing, so let’s see if they can comeback.
Confirmed United squad members
David de Gea, Sergio Romero, Joel Pereira, Antonio Valencia, Matteo Darmian, Axel Tuanzebe, Eric Bailly, Luke Shaw, Michael Carrick, Ander Herrera, Scott McTominay, Jesse Lingard Ashley Young, Juan Mata, Henrikh Mkhitaryan Wayne Rooney, Marcus Rashford, Anthony Martial.