Giggs can now play in several positions as a veteran.
Phelan told manutd.com: "When he was younger, he got away with a lot of things because he was young and he could make mistakes. He was seen as a wide player with great dribbling skills and pace and quality on the ball, whereas now he's brought all those to the fore in different positions. Maturity gives you that.
"In his early career he was surrounded by quality which allowed him to be young, effervescent and show his real qualities, which were his skills. That was accepted by the team, the fans and the club and the excitement he produced when he was young was because he was young, he was capable of making mistakes and he was allowed to make them in order to develop."