Colback is expected to start at Wembley.
He told the Daily Mail: "It's all about what happens on the day. Last year in the FA Cup, they got beaten by Wigan and there's no reason why can't do the same this time.
"We've beaten them three of four times in recent seasons and while other teams have been beaten by them by heavy margins we've managed to get the better of them. It shows we can beat them and it gives us confidence.
"They've got world class players all over the pitch so we know how tough it will be. If we go out with a bit of confidence and play well we could upset the odds.
"It would be massive if we won a trophy. The fans have got memories for 1973. At every club there's a pressure of wining something, even at the likes of Man City or Arsenal. Their fans get to watch good football every week, but they're still desperate for a trophy.
"It's not often an opportunity like this comes along so we'll be absolutely buzzing if we win it."
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