"Michael played very well against Arsenal," says Glenn, "and we know, because the standards he sets are so high, what he is capable of achieving.
"He was not happy with his performances against Charlton and Newcastle, and I spoke to him on Sunday about it - he knows he has fallen below his, and our, expectations.
"He is only just 21, however, and young men of that age can be inconsistent at times.
"He hit the heights against Patrick Vieira, as he often seems to do when he plays against him, and he wants to become more consistent, which we haven't seen over the three games.
"But I have no doubt he will force his way into the England squad. He is a quality player with a lot of strengths which are particularly suited to international football.
"He is looking to push on and fulfil his potential every week, to stamp his authority on all games.
"He knows that, he is capable of doing it, and I am sure he will have a very good season for us. It is a case of waiting for that run of good form to start - and it will do.
"I am a huge fan of his and will help and support him, though at the end of the day you can only give him that stage to perform on. When a player crosses that white line he has to do it for himself, and Michael will.
"He missed the under-21 championships in the summer and was very disappointed about that, but now he is fully recovered - and his best football is ahead of him."
The consolation for Jermain Defoe is a place in England's under21 squad to face Yugoslavia on Friday, and Glenn adds: "I can never understand players that don't want to play for England 'B' or the under-21s, and there have been players in the past who have refused to do that.
"Then they jeopardise their international futures because they are not picked for the squad they want to be in.
"I am sure it is right that Jermain is in the under-21s this season, and he is still playing beyond his age group because he could be in the under-20s.
"I am a believer that players keep to their own age group until it is the right time to move up, as happens in other countries."
As for the trio of players that were selected for the full squad, Glenn says: "I am hopeful that David James starts and it looks as if he has been given his chance to stake a claim to be number one, which has been his aim for years.
"Trevor Sinclair had a terrific World Cup and he won't mind me saying he was the surprise package of it.
"Joe Cole would have liked to have played more in the competition but he has been our best player in all three games this season. He couldn't have done any more and he has got to be happy with his performances even though, like the rest of us, he is not pleased with the results."
Of those results, which see the Hammers bottom of the league at the moment, Glenn says: "People have seen the worst of us in the last 30 minutes of the Newcastle game and in the defending of the two goals on Saturday.
"We are all hugely disappointed. Expectations are high - rightly so - and we have all spoken about it."