They need at least one goal after the 1-1 first-leg draw at the Bernabeu.
With Real trailing Barcelona by 16 points in La Liga, Ronaldo is set to start on the bench this afternoon, though he may get a second-half run-out.
Real travel to Manchester buzzing after beating Barca 3-1 in the midweek Copa Del Rey semi-final at the Nou Camp.
Another win against shell-shocked Barcelona could send the Catalans into a tailspin — but Mourinho knows beating United is far more important given that La Liga is all but over.
Is Mou taking the mick resting Ronaldo? Or is it the right decision? Give us your shout below...