The boss is delighted with the reaction from the boys since that day - a three-game unbeaten run achieved in some style.
"It is credit to everyone working together - the staff, the players," said Glenn. "It can be a stepping stone or a stumbing block, I said to the players that we must make it a stepping stone and progress.
"We had a hell of a long conversation after the United game, we had a good hour. Thankfully they've responded well.
"We've not achieved anything yet, that's for the future. But what we're trying to build I can see it building and I think the players, more inmportantly, can see that. There is players coming back who have not been playing who can see it building and they want to be involved, so that becomes healthy with competition for places."
Glenn went on to confess that he would rather be playing Arsenal than Middlesbrough on Saturday and he views the Boro as a difficult test at this stage.
"This is an important fixture for us, in many ways I would prefer to be playing Arsenal at home rather than our next home game being them because Middlesbrough have got good players and have hit some form themselves and I think this is going to be a tough game for us."
Glenn went on to add that getting results to match performances has instilled an added belief in the squad.
"They have been encouraging. I think at the beginning of the season we had a lot of belief in our performances, but he result didn't come as they perhaps might have come.
"Now, we're still performing at that level, but we've got a bit of belief because we are winning now.
"We've got to maintain that now and that's the hardest task, keeping the standard that we are setting. In the past that is perhaps where Spurs have let themselves down for many, many a year."
Glenn described the shock of squandering a three-goal lead against Manchester United as a stepping stone towards our recent good form, but also admits it could have been a stumbling block.