"We want the players to rise to the challenge," he says. "I have been to Old Trafford many times as a player and I know how difficult it is to get a good result there - but it is always a fixture to look forward to.
"There is no need to be fearful. I always thought that playing them was an opportunity to test your ability against players that are truly international class.
"They have got one or two new players, such as Veron and I'm sure that our players are looking forward to playing against him - they should be, because he is a wonderful player.
"For the Joe Coles, Michael Carricks and Trevor Sinclairs it is an opportunity to see how they compare over 90 minutes.
"Roy Keane is certainly one of the top three outstanding players in British football and it is a chance to see how Carrick and Cole stand up to him.
"Whatever happens we have got to be positive about the game and look forward to it.
"One thing we are going to have to have is a lot of energy because what their players - like all top class ones - have is motivation.
"We have got to match that, and I'm looking for people that have got courage and bravery, people that are going down the tunnel looking forward to the game.
"We need to take some points in what is our toughest month of the season. We play four of the top five teams in the next few weeks, starting with Manchester United and Arsenal, then Liverpool and Leeds on January 1st.
"It is important that we somehow play well enough to pick up the points to keep us away from that bottom three."
He says reports of Manchester United's demise have been greatly exaggerated and adds: "I find it difficult to be commenting about Manchester United's season; they have been such an outstanding team in the Premiership in the last seven or eight years but by their high, high standards I suppose pundits are saying they are not having a good season.
"But anyone who dares to write off their hopes off in the Premiership, I would suggest, is absolutely mad.
"And if they do that would only serve to fire them up even more.
"I have worked with a lot of their players in the England squad and I know how highly motivated they are.
"I'm glad we weren't the next team to play them after they lost to Chelsea; as good as Chelsea are I think that result took everyone's breath away.
"I know how good they are, not only in terms of ability, but as people, and I am looking forward to seeing some of them again.
"It is a great opportunity to see what we are made of; hopefully we can remain tight and work hard for each other and look a solid unit for the 90 minutes - we are going to have to do that to have any chance."
Talking of the Villa game, he says:
"It was a very positive second half but I'm not prepared to disguise the fact that the first half was very disappointing, and if you are going to say well done about the second half we have got to put our hands in the air and say the first half was extremely disappointing.
"After we conceded a bad goal 50 seconds into the game I was disappointed with the lack of responsibility the players took. I felt they shifted the responsibility from themselves to each other, and did not show enough courage or bravery to go and get that goal back that we lost in the first minute.
"Although I think Villa didn't have any real clear cut chances in the first half, we certainly didn't make too many. David James did have to make one outstanding save, a truly magnificent save to keep us in the game, and we managed to get down the tunnel only 1-0 down.
"There was a lot of heated talking to be done at half time and the 15 minutes went very quickly, but when we sent them back down the tunnel for the second half it was a different team with a totally different attitude, and we spent virtually the whole of the second 45 minutes camped in their half.
"I thought where we lacked courage in the first half we showed it in the second and played with a lot of heart and ability, taking the fight to Villa at every opportunity.
"But when those chances kept coming and we kept giving them up I thought it was not going to be our night.
"But thankfully Jermain Defoe, who had his best game for the first team by far, and was one of few positives in the first half, popped up with a goal that was only really a half chance.
"Jermain put in what I would truly call a man's performance and he came of age; but we are not going to get carried away.
"There is an old saying that one swallow does not make a summer but if that is his benchmark from now to the rest of the season, and he will improve, he is going to be a big player for us in the coming seasons.
"I think had Paolo scored with his first chance prior to the penalty or with the penalty itself we would definitely have gone on to win.
"Paolo will lift himself up but after the game he had his head down and was extremely upset. By his high standards, and he would admit this himself, it was an extremely tamely struck penalty but I wouldn't criticise anyone who is brave enough to take penalties in the first place.
"You see penalties missed every weekend on the television but it is particularly annoying when you are 1-0 down and flying at the time."
Glenn laughs off suggestions that Paolo could be returning to Italy and says: "Where in Italy? What clubs in Italy? Where is the gossip coming from? I have not heard anything. Let's make this clear - his contract does not finish this season.
"It is only people whose contract runs out at the end of this season that can talk to clubs on January 1st because they qualify as Bosmans."
Although the player himself has hinted that he would like to talk about a contract extension, Glenn says that for the moment he has to put his energy into getting the side up the table.
"Paolo has still got the best part of 20 months of his contract still to run," he says, "so he has still got one more year after this one.
"The club's policy is that we are only in December and not in a position where we want to sit down and discuss a new contract at this moment.
"That is just the timing, but it is not to say we won't talk to anybody at the end of the season. We are in the midst of a campaign and the timing is not right because there is too much football to be played."
Glenn also says that he will not be taking Spanish central defender Louis Ramis, who has been at the club on trial, on a more permanent deal.
"Ramis did very well in the reserve game but he has an opportunity back in Spain," says Glenn, "and as well as he did, with the players we already have in the squad it was difficult to be able to take him on.
"We have certain players in that position that are on quite long contracts and unless he had been absolutely outstanding it would have been hard - but he did well, and what's more he was a very decent human being."
So the search goes on and Glenn concludes: "We continue to look for players that can go into the first team. I am loathe to fill the squad with players I would be worried about if they went into it.
"It made me smile hearing John Gregory say he was down to bare bones on Wednesday when on the bench he had a £9m striker in Angel, Vassell who you couldn't probably buy, and Ginola.
"I would love to be down to bare bones like that!"