Dyer believes that the Liberty factor - including the boisterous support of the home crowd - could help tip the match against Sir Alex Ferguson's men in their favour.
He said: "I'm sure everyone will be expecting Manchester United to beat us because they have top quality players.
"But we believe in ourselves. We have quality players that have already stood up against some very good teams.
"We are at home, and everyone has seen the impact playing in front of our fans at the Liberty has had.
"They have been fantastic - supporting us home and away, and making us feel like we were at the Liberty even when we were playing at places like the Etihad, Emirates, Stamford Bridge and Anfield.
"With the fans behind us you never know what could happen against United."