Warnock feels his mid-table Championship side have a chance of piling on the misery for Mancini at the Etihad tomorrow.
He said: "According to the bookies we are no-hopers.
"The way I look at it, any kind of positive result will be a bonus. We shall be going there to have a real go at it. We won't be shutting up shop.
"The Cup is City's last opportunity to win something this season, so all the pressure is on them.
"There is always an upset in the Cup. so it might just be our turn to come up with one in this round."