Ferguson has admitted that he may struggle to keep his whole squad happy and left a number of players disappointed after missing out at the Bernabeu.
He told MUTV: "It is very difficult to rotate the squad at the moment. They all wanted to play against Real Madrid and there were a lot of disappointed players.
"That was fantastic. It is a measure of their own confidence in themselves. But we had a chat. I said 'look, don't think for a minute losing a game for Manchester United is a trivial matter'. It is a serious matter.
"The players sense it could be a big year for them. But at this club, in this situation, anything can happen on the run-in. Players can all of a sudden find themselves playing in a final or an important league game because that is the kind of squad I have."
United continued their impressive run of form last weekend with a 2-0 victory over Queens Park Rangers at Loftus Road.