The Red Devils are set to take on the Spanish outfit at the Santiago Bernabeu on Wednesday evening in the first leg of the sides' last-16 tie.
And, with the teams involved having won Europe's premier cup competition 12 times between them, Sir Alex believes that the game is one of the most appealing in world football.
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"I think as soon as the draw was made, there was that anticipation about the tie. It's a fantastic challenge for myself and it should be a fantastic match between two teams and clubs who embrace the best parts of football, with great reputations."
Jose Mourinho's side currently sit 16 points adrift of Barcelona in La Liga and the United boss expects that Los Blancos will be solely focused on winning the competition for the 10th time for that reason.
"I think Jose has set his targets firmly on the European Cup, no doubt about that," he declared.
"It can be hard for us but there's a bit of pressure for them, too. At this moment in time, we're involved in three [competitions]."