Danny Lennon insists lighting can "strike twice" to see St Mirren shatter Celtic's cup dreams for the second time this season.
The Buddies, who beat Celtic in January's League Cup semi-final, host the SPL leaders in the last eight of the Scottish Cup.
"The romance of the cup is something very special for us and hopefully we can progress," Lennon told BBC Scotland.
"We're having a terrific run."
Lennon is unfazed that his side go into the side as underdogs, despite winning their League Cup tie at Hampden two months ago.
"We're going to face the best team in the country and will have to be at our best," he said.
"Many so-called experts have already written us off and say that lightning can't strike twice but it can; it's rare but it happens.
"These are the same experts that said we couldn't go to Hampden and beat Celtic in the League Cup semi-final but we did that.
"The last time we played, we were more than a match for them and we can take great confidence from that."