The reigning Premier League champions have put up a limp defence of their title, lying in seventh place with five games left to play and almost certain to miss out on qualification for the Champions League.
|MAN UTD PREMIER LEAGUE RECORD
"We have to be together," the Spain international told the Daily Mirror. "Now is not the time to blame anyone. Now is not the time to look for guilty people.
"Now is the time to stick together - with the manager, with his staff, the players and with the people on the board of the club. We need to carry on, to stay with the manager. We need to believe in him because, as players, we know we have to improve.
"It's not just the manager, it's not just the tactics. It's all of us. It's not the time to blame one person. We are all together in this.
"Some of my friends told me, if this situation was happening in another club in Spain, it would be different but the club and the players are behind the manager.
"We need to be strong as a team, as a dressing-room, and keep working hard. We need to improve, we know it, but we need to do it together."
Goal revealed on Wednesday that Moyes had travelled to Portugal to watch Porto take on Benfica and assessed a number of scouting targets, including Jackson Martinez, and Mata has now revealed that, when discussing the move to United, he was told that the club would make significant moves in the transfer market as they look to rebuild the side.
"When I joined, in all my conversations with the board and the manager about next season, they were confident about getting the right players," the attacker recalled.
"They know, and I know, we're in a transitional moment but, in the summer, they're going to try to sign a few players and I have the faith they are going to bring top players in.
"I'm sure this club is going to come back and fight for every trophy. Since I was a kid, Manchester United was fighting for everything and this moment is going to come back for sure."