The official was knocked out after a coming together with the Benfica defender, who is facing calls for a lengthy ban for his part.
The Benfica stopper was left frustrated when the official showed two quickfire yellow cards to Javi Garcia. As Luisao made his feelings known, there was a coming together of the referee and the Brazilian defender in a clash which left the official unconscious.
Fischer has now spoken out about the incident, saying that he had not expected anything like that to happen.
"I did not see the player who bumped into me coming," he is quoted as saying by Sport1. "I wanted to book a different player for a second time, and suddenly two Benfica players were surrounding me.
"It was like running against a brick wall at full speed."
Luisao claimed in the wake of the incident that he had no reason to feel guilty, and asserted his innocence. However, Rainer Koch, an official from the German Football Federation (DFB) has called on the Portuguese FA to punish the defender heavily.
"The Portuguese FA has the authority in that case. There can only be a harsh penalty for such incidents. Attacks on the referee are absolutely unacceptable," said Koch.
"There has to be zero tolerance in such cases. I expect the Portuguese FA to take drastic action and ban the player for quite a while - not just for a few matches."
Follow GOAL.COM USA on