Mirallas was outstanding in the Liverpool derby before being forced off at halftime due to injury.
"Kevin has gives us another dimension," said Moyes, who beat off competition from Porto and Arsenal to sign the 24-year-old. "I'm surprised, if I'm honest, at how quickly he's settled in, because I was worried at the start of the season he wasn't ready to play 90 minutes in the Premier League.
"Yet he seemed to relish the challenge in the derby and in some of the tough away games we have had there have been real signs. You can see he can be a top, top player. His record of scoring goals is really good too, and I think there is that to come from him.
"Maybe in the second half of the season we'll see that from him. He can play in any of the three positions across the front line. I like that about us: we have some versatility, because (Steven) Pienaar can play in different positions too and we want options and alternatives.
"We want to ensure we are not one-dimensional in games. Kevin is coming to terms with the Premier League now. Every single game here you have to grind out a result. Maybe where he has played before, there have been a few 'gimmes' when you can ease off. You can't do that here."