Quins, who are the top seeds in the tournament after winning all of their pool-stage games, face the Irish side at The Stoop on Sunday.
The club's director of rugby told BBC London: "They are a good side and this is cup rugby now. There is no other chance. That fear brings out different things in people.
"Hopefully we can control that fear and put in our ambition. We want to play, that is the way this team is built.
"We said coming out of the pool we don't care who we play against. It is tough to play Munster at any time but we just want to get out there."
Harlequins have never won the tournament.