The Hoops manager at times conducted a verbal battle with some St Mirren supporters behind the dugout during a fast-paced encounter which saw Joe Ledley open the scoring in the fifth minute with a header before a mistake by Celtic left-back Emilio Izaguirre in the 13th minute allowed Esmael Goncalves an easy chance to level.
Anthony Stokes restored the visitors' lead in the 21st minute with a close-range header which, ultimately, was enough to put the Parkhead men into Monday's semi-final draw at Hampden.
"It was from the first whistle really, just a bit of banter really, nothing over the top," he said. "Nothing new there in Scotland. In fact, the timing of one of the boys' shouts was perfect.
"He said, 'Hey Lennon, you will get the sack in the morning' just as Joe Ledley scored, so it was marvellous. I am delighted, we deserved to win the game.
"The equaliser was a comedy of errors and we have to stop doing that. We were so much in control of the game, St Mirren did nothing to warrant them getting back into it and we gift-wrapped them the goal. But our recovery was excellent."
After beating Celtic in the Scottish Communities League Cup semi-final at Hampden in January, Saints boss Danny Lennon was looking for lightning to strike twice.
He said: "It didn't but we came close to it. I am very proud of the group of players.
"We got off to a poor start but to get ourselves back into the game was pleasing and then we lose another poor goal from another set-play.
"Graham Carey had a terrific free-kick and there was a save to match it and then Sam Parkin should have done slightly better and the ball fell to Lee Mair who hit the side-netting."
- Sports & Recreation
- Joe Ledley
- St Mirren
- Emilio Izaguirre
- Anthony Stokes