Aside Okafor, other goals from the match came from Tijjani Reijnders, and debutant Jan Carlo Simic.
However, despite the convincing win, Milan faced setbacks with two additional muscular injuries that includes Okafor.
Reijnders broke the deadlock scoring navigating through five defenders to slot in the ball past Monza’s goalkeeper Michele Di Gregorio.
The Rossoneri’s attacks continued as debutant Simic, capitalized on a Rafael Leao assist, securing the second goal for the host, then was denied from a corner kick.
Series of remarkable saves by Di Gregorio denied Alessandro Florenzi’s long-range efforts.
Milan’s third goal came with a combination of team efforts. Reijnders started the move, deleting defenders to deliver a flicked pass to Olivier Giroud.
Giroud, with a deft touch, set up Okafor, who elegantly slotted the ball into the bottom corner.
However, the celebration was short lived as Okafor suffered a thigh injury, forcing an early exit after a brief 10-minute appearance.