The 25-year-old World Cup winner was voted Chelsea's Player of the Year for two consecutive seasons but his chances were limited under returning manager Jose Mourinho, prompting his club-record move to Old Trafford on Saturday.
Speaking to the media following a press conference at the Aon Training Complex on Monday, Moyes was delighted by his January acquisition and hailed the Spaniard's attitude to the game.
"He is a top player, he has proved it," Moyes said. "He is confident because of what he has done over recent seasons. I don't think there is any football fan who watches the Premier League who wouldn't have admired Juan Mata in recent seasons because of the goals he has scored and the goals he has made. Yes, he is confident. He has come to a club that is delighted to have him.
"I don't know him well enough yet to put words like great next to his name. Everybody who tells me about him says he is a great ambassador for football. He conducts himself very well. He is a smart, intelligent young man. From what we have seen he is all of that.
"He understands the club he is coming to. He is a Spanish international who wants to play to make sure he is in the World Cup squad. I think he can genuinely add something to what we have got. He can give us a different type of player to