He told the Sunday Mirror: "We need to pile on more misery for Liverpool. They might be missing their two best players - Gerrard and Torres - and hopefully we can cause an upset. In their fans' eyes they need to win every game at Anfield.
"If they don't they get disappointed."
Benitez's side have won just once in their last eight games - and now need a miracle to progress in the Champions League after drawing at Lyon.
McFadden, who cost Birmingham £5million, added: "The Everton-Liverpool thing is still there for me. I was there for nearly five years and it was a great time in my life. Obviously I've still got an affection for Everton. That means I want to do well against Liverpool. I was fortunate to play in a Merseyside derby against Liverpool at Anfield and, although we lost, it was a good experience for me.
"Historically, Liverpool are a big club. It will be nice to go there. The way we've played in the last few weeks we think we can get something out of the game. I still have the banter with Liverpool players and their fans. And my mates at Everton will send me a few texts if we do well.
"But first and foremost I want to do well for Birmingham City. I think Benitez has done a good job at Liverpool, but all the talk is about the manager being under pressure. We're going there believing we can win the game."