Arsenal manager Arsene Wenger says failing to qualify for next season's Champions League would bring dramatic consequences.
The Gunners will qualify directly into next season's Champions League group stage if they finish in the top three, hence avoiding the additional pressure of having to feature in the play-off stage.
And the Frenchman is desperate to avoid this scenario.
"We feel we have made progress, but we have a good opportunity to show that on Sunday because in every game that is questioned," Wenger said on Friday.
"Only one thing shows you have made progress and that is the continuity in your performances, and that you have a good level of cohesion.
"I believe as well that the way we respond to our disappointment on Monday night is a big indication of how strong we are.
"It's very important for your season preparations to not have that kind of stress [about the Champions League qualifier] over your head from the first day you start again - it's vital. The consequences are always dramatic if you don't qualify.
"[A win against Manchester United would] mathematically put a distance between [them] and us in the top four and basically secure the top three.
"Also, we can make a symbolic statement because we won over there in the FA Cup. To reproduce that would be psychologically important."