He hopes this week's official, Steve Bennett, and his team are spot on, while acknowledging the demands placed on them in what will surely be a keenly contested clash - with both sides knowing a defeat will lead to a bottom placing over Christmas.
Looking back to last weekend, Glenn says: "We've gone through the video a couple of times and there are periods in the game where we have played very well, but there are obviously turning points.
"Those didn't go in our favour against a Manchester United team that, I have to say, also had their periods where they had us on the rack.
"Then again, they did the same to Arsenal and Deportivo - so we were playing a team that has got a full head of steam on at the moment.
"But going back to ourselves, the game, and turning points not being in our favour, I have no doubt that Phil Neville does knock over Jermain Defoe in the penalty box; it is clear he takes him out at the thigh after one minute.
"I understand this much - you do need a referee to be brave and Mr. Styles would have had to have been very brave there.
"But you rely on a referee to be strong and brave - he has got a great view and it does make me think that at Old Trafford in the first minute we are never going to get it.
"At the time you are not sure but when you see it on the video, and in slow motion, it is nailed on."
To make matters worse, at the other end of the first half Jermain was denied a goal because of the linesman's flag.
"We only made a couple of half chances in the first half but when the clear cut chance comes along Jermain finishes really well - and you get let down by the linesman," says Glenn.
"It is very frustrating because John O' Shea, who is playing Jermain onside by about three or four yards, is literally in front of the linesman - and he must have seen it.
"He had to keep his flag down, but he didn't, and although we could still have lost the game, the atmosphere in the dressing room at half time would have been a whole lot better having just scored at Old Trafford - and no one knows what would have happened then.
"It is the second time this year that Defoe has had a good goal ruled out. At Fulham he scored a fantastic goal against Fulham with a great strike, when he clearly ran from an onside position.
"You do need people to do their jobs and get it right more than they get it wrong - and just at the moment we don't seem to be getting the rub of the green.
"Decisions like that can make a huge difference to your season and you do need them to get it right.
"I know the game is getting quicker and quicker and perhaps more difficult, but that is their chosen job, what they want to do, and they have to get the decisions correct because it is so important to everybody."
Of Manchester United's three goals, he adds: "I was a little disappointed with the first goal. Solksjaer's header would have either drifted into David James' hands or even wide, but it took a heavy deflection of Tomas Repka's arm which completely changed the direction of the ball to deceive David.
"Veron's free kick was fantastic technique - he generated good power from a long way out and within 90 seconds we were two down.
"But the boys kept playing and David James had to make one good save in the first half when Van Nistelrooy came inside Christian Dailly but we kept going and played some good football, shifting the ball well.
"In the second half we didn't fold and conceded an unlucky own goal off Sebastien Schemmel, and finished quite strongly in the last 15 minutes.
"The game was lost by then, but I can't complain about how much effort the boys put in, like they have done over the last four or five weeks."