"It's a no-lose situation for Cardiff because they are not expected to win," said the former Liverpool striker. "But deep down I think the supporters, the players and the manager will think if they can get it together and Liverpool don't, they could win it.
"If you get to any final there is no easy ride. It's what you make of it," said Rush, the League Cup's joint top-scorer with Sir Geoff Hurst on 49 goals.
"Yes, Liverpool are favourites to win but if they go about it with the wrong preparation they are in for a big shock. Cardiff are capable of beating any side on the day.
"This is why cup finals are so special because on the day anyone can beat anyone.
"That's what it's all about and that's why for me the FA Cup and the Carling Cup are the best cups in the world. That's the beauty of the cup."