Blues have won their last two games in the Carling and FA cups, scoring three goals in each outing.
However, they currently lie in 17th place in the Premier League, having picked up just one point from their previous three league matches, the last of which saw them lose 5-0 to Manchester United.
McLeish is hoping their new-found potency, together with the new faces brought in during the January transfer window, will help them play with more freedom.
"The target for us is to get up that table," the Blues boss said.
"A couple of wins and cup-like performances will do nicely. The factor that should register with the players is the confidence that has been gained from the cup performances.
"We want to make it as much of a nightmare for the opposition as we can. Maybe now we've got more of a potent mix up front we can have a right go."
Source: PA
Source: PA