After losing arguably their best player Paul Pogba to suspension, the odds against United qualifying are stacked quite high. No club has ever progressed to the next round of the Champions League after losing the first leg of a knockout match at home by two or more goals.
What does Ole Gunnar Solskjaer need to do to overturn the tie? Is it an impossible task?
In Pogba, United have lost their most creative player and their best ball-carrier.
The Red Devils have their system centred around the World Cup winner and hence, need to tweak it up to make up for his absence.
United have good attacking depth with the likes of Romelu Lukaku and Marcus Rashford despite concerns over the fitness of Jesse Lingard, Anthony Martial, Juan Mata and Alexis Sanchez. Not to mention the injuries to key midfielders Nemanja Matic and Ander Herrera.
Solskjaer has no option to start with an in-form Romelu Lukaku and Marcus Rashford. There is a possibility that Diogo Dalot might be positioned in an advance role, given the injury worries.
Advancing full-backs is another way United can show their intent to draw blood. Solskjaer will expect Luke Shaw and Ashley Young to carry a menace on the wings.
Yet again, they will be compromising on the defence by doing so, especially with Kylian Mbappe waiting to pounce on the counter. But this is a chance they will have to take, should they advance to the quarter-finals.
Will the Norwegian opt to go all out against PSG, or will he adopt a more conservative approach and strike at the right time? Losing the players who can control the tempo of the game to suspensions and injuries points to the fact that Solskjaer is better off choosing the former option.
"We have done fantastically well away from home but we go to PSG with the belief, we have nothing to lose. We will give it a go. This club has done so many great comebacks, the tie is not done," Solskjaer said.
"The dressing room is bouncing at the moment."
United will have to keep a high intensity for 90 minutes for this to work out in their favour. But ultimately, this is their best shot.