Referee Angel Sanchez told Portuguese state radio on Saturday that Joao Pinto punched him after he sent the Portuguese forward off in a World Cup group D match against South Korea.
"He punched me on the left, in the ribs," Sanchez told RDP in an interview.
Portuguese players had to separate and calm down Joao Pinto after the Argentine referee showed him a red card for his tackle from behind in the 27th minute on Park Ji-sung on Friday.
Portugal captain and defender Fernando Couto held Sanchez by the face as the Portuguese players argued with the referee over the decision.
Sanchez said Eusebio approached him after the game to apologise on Joao Pinto's behalf.
"A player as important as Eusebio told me that he had known Joao Pinto since he was a boy, and came to ask me not to report what I had to report," Sanchez added.
Portugal had another player sent off, Beto Severo, in the second half and lost the match 1-0, after which the team failed to qualify for the second round of the tournament.