Ronaldo has recommended that Zidane be considered as a potential alternative in the dugout.
He reportedly told friends at the time that he wanted to become United’s next boss if Mourinho was sacked.
With both Atletico and Real’s games kicking off at 18:00 SAST, it points to an exciting end to the season.
The tie is delicately poised following a 1-1 draw at the Estadio Alfredo Di Stefano last week.
They created enough chances to have clawed back the two-goal deficit but goalkeeper Thibaut Courtois was hardly extended.
Madrid’s entire XI in Italy had a paltry three goals in the competition this season between them at kick-off.