Instead Madrid had Diego Lopez between the sticks, signed in January as a short-term solution after Casillas had been struck by injury.
Ferguson was more than forthcoming in his praise of Lopez, crediting him as the real reason why United did not win. In addition to the referee of course...
"Diego López was the difference. I would have preferred Casillas.
"Iker wouldn't have saved the shots that the boy López did. Going out to Danny Welbeck in the first half, going down at Robin van Persie's feet, coming out and whacking Nemanja Vidic in the head... Casillas isn't that type of goalkeeper."
Not many managers would prefer to face Madrid team with the goalkeeper voted as the FIFPro World XI's number one in goal, but Ferguson certainly regrets the Spanish international's omission.
His comments are interesting, and Ferguson will no doubt always be left wondering 'what if?'.
He has a point in that Casillas and Lopez are differing goalkeepers in terms of style, but for all he knows Casillas would have come out and claimed the cross at the Bernabeu which led to Danny Welbeck heading home.
Both goalkeepers are top class, and United only have themselves to blame for not finding a way past Lopez on more occasions than they did, relying on an own goal and a set piece.
What do you think of Ferguson's comments? Would United have won if Madrid had Casillas in goal?
image: © jansolo09