Borussia Dortmund will be without England winger Jadon Sancho as they face a "brutally difficult" task of overturning a 2-1 deficit in Germany.
City scored a late winner in the first leg of their Champions League quarter-final, leaving the Bundesliga side with an uphill task.
And Dortmund coach Edin Terzic is well aware of the challenge his side faces.
Opinion: Could Rashford and Sancho stop people hating Man Utd?
"Belief is big but belief alone will not be enough," Terzic told a virtual news conference on Tuesday. "We played a good game last week and showed we can keep pace with a top team.
"It was frustrating that we conceded a late goal. So now we cannot focus just on defence. We have to be attacking. It will be a brutally difficult task. So believing is not enough. We also need hard work.
"It's is about showing we can play against the best team in the world and maybe eliminate the best team in the world from the competition."
Phil Foden entschied das Viertelfinal-Hinspiel in der Champions League gegen Borussia Dortmund
Image credit: Getty Images
To add insult to injury, Dortmund will be without former Manchester City winger Sancho, who has been sidelined since early March.
Mats Hummels and Marco Reus, who have also suffered knocks, will be assessed ahead of Wednesday's match.
'This is where I belong' - Man Utd confirm Sancho transfer
Pogba rejects £350,000-a-week deal offer from Man Utd - reports