Ole Gunnar Solskjaer's men head to Paris St Germain for the second leg of their last-16 tie on Wednesday evening trailing 2-0 after a humbling experience at Old Trafford last month in what remains the only defeat they have suffered to date under their interim manager.
PSG will run out as hot favourites to progress to the quarter-finals, but 33-year-old Young has advised them to take nothing for granted after seeing his team-mates revive their season since the Norwegian's arrival.
He said: "We know what we're capable of. People can write us off. People were writing us off at the start of the season and people are writing us off now. It's no different.
"Obviously it's going to be tough. It's not going to be easy. We've got to go over there, win the game and score goals.
"I've got every faith if we defend well and if we create the chances that I know we can do, we can win the game."
Asked what United need to do better to turn the tie around, Young added: "Win the game.
"That's exactly what it is. We've got to go out there and win the game. We can't worry too much about them, it's all about us."
No Pogba in Paris
Paul Pogba's red card in the first game means he is unavailable for the return, a major loss given his resurgence in recent months, while the names of fellow midfielders Nemanja Matic, Ander Herrera, Juan Mata and Jesse Lingard appear on a casualty list which also includes Phil Jones, Matteo Darmian, Phil Jones, Antonio Valencia, Anthony Martial and Alexis Sanchez.
However, Young is confident the spirit which fuelled Saturday's 3-2 fightback victory over lowly Southampton will serve his team well once again.
He said: "That's the club's way, the United way. Never say die."
If the odds are stacked against United, Solskjaer at least has striker Romelu Lukaku back in lethal form in front of goal after he claimed a fine double to help see off the Saints.
The Belgium international has scored four times in his last two outings after a nine-game barren run to underline his enduring quality.
Young said: "I wouldn't want to play against him. He does give us a different presence.
"It's good to see all the strikers in form, the whole team. It's not just 11 men on the pitch, it's a squad game.
"Everyone has got to be ready. Everyone has got to be prepared and ready to play when the manager calls on you. When you've got competition for places, it can only help."
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