Los Blancos offloaded the Portuguese superstar to Juventus in the summer and have struggled without their talisman.
Julen Lopetegui was dismissed after a dismal run of form.
And, while Santiago Solari has now steadied the ship, performances haven’t been wholly convincing.
Courtois arrived from Chelsea during the last transfer window and has labelled Ronaldo ‘irreplaceable’.
However, the Belgian goalkeeper has urged his Real team-mates to step up.
“Cristiano Ronaldo is irreplaceable, you cannot forget what he did,” Courtois said.
“But he is not here anymore, so it’s time for other players, like Bale did in the semi-finals [of the Club World Cup], to score the goals he [Ronaldo] used to score.
“If we are able to do so, it’ll be fine.”
Real’s title prospects already look very slim.
They are a whopping eight points off pace setters Barcelona.
It’s not all doom and gloom at the La Liga giants though.
Real secured a record-breaking Club World Cup triumph with a 4-1 win over Al Ain in Abu Dhabi on Saturday.
Speaking after the clash, Solari hailed the work of Zinedine Zidane.
“We are happy, these players deserve it,” Solari said.
“They have come here after a lot of work and a lot of wins.
“We put a finishing touch to that third consecutive Champions League, it is a feat of the club, this group and other coaches.
“We are also here thanks to Zidane.
“It will be difficult to match in the future.”
Real face Villarreal in La Liga after the festive break.
The Yellow Submarine are having a turgid season and sit third from bottom with 16 games played.