The midfielder made his debut as the Reds ran out 2-0 winners over Cardiff on Tuesday evening, and provided the assist for Ashley Young's second-half strike. Moyes was impressed with Mata's contribution, and says his arrival gives him more options for the remainder of the season.
The manager said: "I can play him in any role. He can play off the left or off the right, which allows me to keep the Rooney-van Persie partnership. I'm quite comfortable with that, and he’s also capable of doing another job like the no.10 role. Wayne has dropped into midfield in some games, so we've got options.
"I know we can use Juan in different positions - I think what he'll do [wherever he plays] is take the ball. We'll get used to him and he'll get used to us. Mata scores goals and creates chances, and you can't get enough of those, especially at Old Trafford.
"Now we've got competition, I can use the players at different times and change them within games if we need to do that. I wanted to see Juan play with Robin and it was good to get him those minutes.
"The crowd gave him a fantastic reception. They saw he was creative in the early part of the game and he probably made our best chances in the first 20 or 30 minutes."