Mazraoui started the game at right-back, with African Player of the Year Achraf Hakimi an unused substitute as he recovers from injury.
The United defender saw plenty of the ball, having 93 touches as the hosts pinned back their Group A opponents.
He contributed an assist early in the second half, with his cutback tucked home by former Manchester City forward Brahim Diaz, and then tested goalkeeper Yannick Pandor with an effort of his own.
The win was sealed via Ayoub El Kaabi’s spectacular overhead kick 15 minutes from time, at the impressive new Prince Moulay Abdellah Stadium in Rabat.