Moyes brought Mata to Old Trafford for a club record £37.1 million in the January transfer window - the biggest single deal of the month anywhere in Europe.
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Asked if they are the best attacking trio in the Premier League, he replied: "I think they will be when we get them ready and totally match fit all of them and gelled together.
"We need to give Juan Mata time to settle in and not get too far ahead of ourselves too quickly.
"The one good thing is that because he has Premier League experience and being in the league and being at a big club, coming here should be a little easier.
"But we still have to be mindful that there is a change and we have to give him time for that to happen."
Moyes believes the players' ability to switch positions will make them an extra threat for defences.
"Football is changing as the game goes on. Players change themselves," he added during his weekly press conference.
"There is a lot more movement especially with the forward players. They still have to play in a framework and from that framework you allow it to develop themselves."
Goal revealed in December that Van Persie is telling Moyes and the United coaches when he feels fit to play, something the manager now confirms.
"I have taken Robin's advice on where he feels he is at, if he is ready to play and how long he feels he is able to play," he continued.
"All the things I am doing I am taking from Robin. He is a player who is so important to us. I need to know exactly where he is at."