The 19-year-old has become a regular member of the Red Devils squad, as well as an England international, in less than two years.
Last season, the forward scored seven goals and produced three assists across the Premier League and Europe, and in the current campaign the teenager has six goals and four assists in all competitions so far.
"Marcus has had a fantastic start to his career. He now has to go onto that next level and keep learning in every training session and every game," Giggs told Sky Sports News.
"Marcus is one of those players who - I have been to Old Trafford a couple of times this season - as soon as he gets the ball you can feel it in the crowd. You can feel the excitement. He gets you off the edge of your seat."
The United academy graduate has largely been deployed on the left-hand side of attack by manager Jose Mourinho this season.