The friendly match between Fortuna Dusseldorf and Benfica was abandoned on Saturday after the referee was pushed over by Luisao.
Before half-time referee Christian Fischer was about to hand a second booking to Benfica midfielder Javi Garcia when Luisao stormed torwards him and pushed him down, according to reports from Rheinische Post.
The ref was in a daze for a few minutes, before abandoning the match after 43 minutes and leaving the field for treatment by Dusseldorf's team doctor.
Speaking to Rheinische Post, Dusseldorf chairman Peter Frymuth explained: "The ref was attacked and had to be treated by our doctors inside the locker room. Because of that attack the game was abandoned.
"This should have been a day of celebration for us, but now it has becoming a depressing affair. We are sick at heart."
Frymuth added Dusseldorf would approach UEFA over the event.