Stale Solbakken said Copenhagen needed to be "perfect" to have any chance of upsetting Manchester United in the Europa League.
The Danish side face United in the quarter-finals in Cologne on Monday looking to cause a huge shock.
As they prepare for the 2020-21 Superliga season, Copenhagen overcame Istanbul Basaksehir in the last 16, recording a 3-0 second-leg win on Wednesday.
But Solbakken said only perfection would be enough for his side against United, who have lost just one of their past 23 games.
"In order to [beat United] we have to play perfect, we need a bit of luck. We maybe need a United that doesn't fire on all cylinders," he told a news conference.
"We need to be perfect defensively. We need to take one or two or three chances we get during a game like this. The chances are not great, but it's an advantage for us that it is over 90 minutes and not 180 minutes.
"But we have a good feeling after the season we had a week's break and when the players returned from that we were able to get a couple of players ready to play that were vital to us before.
"We have a good feeling after the 3-0 victory, but you should not put your house on us. We'll give everything."