The Real Madrid defender was dismissed during his side's 2-0 win over Rayo on Saturday, and suggested his reputation may have preceded him
The Spain international received two yellow cards withing minutes of one another after scoring his side's second goal, and felt guilty about letting down his team-mates.
"I am hurt by the situation," he was quoted as saying by AS.
"It is not normal for me to be sent off within two minutes. I'm not one to come in with hard tackles or to do something evil. It's easy to send off Sergio Ramos. It's worrying.
"It hurts me to have left my team-mates disadvantaged and to have forced changes. Spanish football deserves the best referees because we have the biggest players.
"Referees are required to interpret situations. My first card was completely unfair. You cannot leave a team with 10 men for that."
Madrid recorded 1-1 home draw in the first legs of their Copa del Rey semi-final with Barcelona and their Champions League last-16 tie with Manchester United, and Ramos is aware of the return fixtures' significance.
"The two games are hugely important," he said. "We are the first ones to be convinced that we can progress in the Copa and in the Champions League."