The Brazil international feels referee Miguel Ayza was wrong to dismiss the forward during Real Madrid's 1-1 draw with Athletic Bilbao
The Portugal international was dismissed after he got involved in a scuffle with Carlos Gurpegui and Ander Iturraspe in the 76th minute, but Marcelo feels his team-mate did not deserve a red card for his actions.
"It is tough to lose a player unfairly," Marcelo told the club's website.
"Cristiano’s sending off was unfair, but I am not going to talk about whether the referee had a good match or not."
The left-back stressed that even though Madrid always aim to win, a draw in Bilbao was still a good result for los Blancos.
"We won a point, which is very difficult here, but our mentality is to win every match," Marcelo continued.
"It is not always possible and we kept going until the end. Athletic Bilbao are a good team but we were unlucky and it’s a shame."
Madrid currently sit third in La Liga, trailing leaders Atletico Madrid by three points.