While an angry Neil Lennon and Anthony Stokes recover from the shock of yesterday's semi-final defeat, Jim Goodwin, Graham Carey and David van Zanten can look forward to the biggest day of their career.
All three started their careers at Celtic but none managed a 90-minute first-team appearance before moving on.
Former U21 skipper Goodwin has spent the bulk of his career at clubs such as Stockport and Huddersfield but will return to Hampden on March 17 to lead the Paisley side against Hearts with a genuine chance of winning the club's first trophy since 1987.
St Mirren were 7/1 outsiders going to Hampden yesterday with too many Celtic players believing that the domestic treble was a formality.
Straight from the kick-off the Paisley side were sharper in movement and thought and were unlucky to go in level at the interval after Gary Hooper equalised an early strike from debutant Esmael Goncalves.
After Charlie Mulgrew missed a penalty, former Celt Paul McGowan made no mistake at the other end with Stevie Thompson putting the result beyond Celtic, although Mulgrew netted with the last kick of the ball.
St Mirren boss Danny Lennon said: "What had inspired me was a fan had put a lovely montage on YouTube and it was so that we could believe. I'd been shown it prior to the Ross County game last weekend. It went way back to 1959 and it showed other great results. It was something we looked into.
"When you come into these games you'll try anything, you'll try something different and they didn't let us down.
"It was a fantastic effort from everyone and I'm absolutely delighted for the fans.
"I could hear them throughout the game and hopefully we'll start to see those crowds coming back regularly at Paisley and that was a thank you to them."
His opposite number was less than thrilled by his players, branding them spoiled kids, as he watched in frustration from the sidelines.
"I'm bitterly disappointed with that performance," said Lennon. "It was soulless, it lacked intensity, it lacked desire, it lacked will to win. It lacked all of the attributes this team has shown over the last six to nine months. Our reaction was poor from the second and third goals onwards.
"There was a lack of discipline in our shape and a lack of discipline in our play and some of them behaved like spoiled kids.
"I've dealt with it in the dressing room and I'm not going to speak about it again to the players. The treble is gone and we have only ourselves to blame."