"It's the same with these young lads. They have to keep believing in themselves and, when their chance comes, take it. And they will get chances."
Sir Alex revealed he hopes to hand opportunities to almost a dozen Reserves or fringe players, including Gerard Pique, Chris Eagles and Tomasz Kuszczak. He also said Nani, Anderson and John O'Shea could be involved.
"This is a really important night for these players. They all want regular first-team football and that's not easy to manage. I'm trying to get them games in the Premier League and in Europe too, but Wednesday is a great opportunity for them.
"You have to use your squad throughout the course of the season and I'll be doing that when the time's right. At the moment they might not see that, but it will happen and I know they won't let us down.
"A lot of these players have already shown great improvement. Chris Eagles has been sensational in training and the games he's played in. Young Jonny Evans and Gerard Pique have also been excellent, as has Danny Simpson.
"There's real promise there and that's what we want to see on Wednesday. We want them to play with the kind of commitment they see from the first-team players every week."