Manchester City boss Roberto Mancini feels Real Madrid will end Manchester United's Treble hopes on Tuesday.
Real are at United in the second-leg of their Champions League tie.
Mancini said: "I don't know. I think that Real Madrid, for me, are the best team with Barca at this moment and it will be hard for Manchester United.
"They played well in Madrid. In this game, I think everything is possible, all results."