Ronaldo was sent off on a straight red card for punching and kicking defender Edimar inside Cordoba's penalty area during a Spanish league clash.
Ronaldo apologized on his Twitter account saying, "I ask forgiveness from everyone, especially Edimar, for my thoughtless act."
"Those of us playing as forwards are exposed to provocations and intimidation and sometimes you lose your nerve," Neymar said.
"It's clear we cannot do that under any circumstances. He must be punished because of the aggression."
If Ronaldo is given a three-match ban, he will miss scheduled matches against Real Sociedad and Atletico Madrid and a postponed round-16 match against Sevilla.