The Australian international midfielder, who played a big part in the Socceroos' march to the last-16 at the 2022 World Cup, delivered the corner after just 96 seconds on Sunday that Marcus Fraser nodded home to give the Saints a sensational lead at Hampden Park.
It ignited a famous win for the Paisley underdogs with Kenyan international Jonah Ayunga proving the hero with his second-half brace to earn St Mirren their first silverware in a dozen years.
It was only their fifth major trophy in their 148-year existence and made it a nightmare start for Celtic's new coach Wilfred Nancy, who's lost all his matches since he came on board at the start of the month following the resignation of Brendan Rodgers and the successful interim reign of Martin O'Neill.Â
For the 27-year-old Baccus, though, it felt one of the crowning moments of his career and a reward for returning to the club in August after he'd left St Mirren in 2024 seeking to forge a fresh career across the border with English League One side Mansfield.
He reckoned the win ranked up there with his World Cup odyssey in Qatar, as he reflected emotionally on having first taken a gamble to come to play for the Saints back in 2022 after having previously excelled in over 100 games for Western Sydney Wanderers.
"I feel amazing, I can't remember the last trophy I won. I'm lost for words," the defensive midfield told BBC Scotland after being unsure originally if he would start the match until manager Stephen Robinson gave him the nod.
"I left Australia to come here and it's been such a big grind. I'm just so glad I came back to the club.
"The fans are amazing, they're like a 12th man. I thank the club, God, my family. I'm just so proud of everyone involved."
After the Saints' early goal, Celtic had equalised in the 23rd minute through Reo Hatate, with most of the 50,000 crowd expecting that to be the signal for Celtic to take control.
Instead, the champions dropped off, and in the second half Ayunga netted from a cross and then a counter-attack in the space of 13 minutes for "the Buddies" to pull off a win that was greeted with ecstatic celebrations.
"We played with no fear, all faith. We didn't crumble when they scored," enthused Baccus.
"This is up there with the World Cup, for sure."
