Semi-finalists in both domestic cup competitions last season, Jim Goodwin’s side already look good for a place in the knockout stages of this tournament once more.
Their campaign began without kicking a ball last Saturday when they were awarded a 3-0 win over Dumbarton who were unable to fulfil the fixture because of Covid issues.
With Dunfermline having kicked off with an impressive 4-2 win at Partick Thistle, this already had the feel of a potentially decisive contest and it was the Premiership outfit who deserved to prevail.
Even the welcome return of some supporters to St Mirren Park, around 500 of them spaced out around the stadium, couldn’t create sufficient volume of atmosphere to drown out two of Scottish football’s more vociferous managers.
As they prowled their respective technical areas barking out orders and gesticulating to their players, the animated duo of Goodwin and Pars boss Peter Grant provided as much entertainment as anything on the pitch in the early stages.
Dunfermline produced some passing football which was pleasing on the eye, keeping possession with precision and confidence for spells but without finding the kind of penetration necessary to trouble the home defence.
By contrast, St Mirren carried more of a threat during the periods when they dominated territory.
Dunfermline goalkeeper Owain Fon Williams was forced into the first save of the night, the big Welshman reacting smartly to touch over a rising shot from Scott Tanser whose initial effort from a free-kick had been blocked by the defensive wall.
But Williams was powerless to prevent Saints’ breakthrough as former Motherwell and Aberdeen front man Main got off to the perfect start with his new club. Greg Kiltie, one of his fellow summer recruits, provided the inviting cross from the right and Main met it with a precise header which beat Williams to his right.
St Mirren captain Joe Shaughnessy might have doubled the lead four minutes before the break, heading over from a Jamie McGrath corner, and there was no doubt the hosts merited their half-time advantage.
The potency Dunfermline had shown in their win at Thistle continued to elude them after the break with striker Nikolay Todorov unable to react sharply enough to convert from the edge of the six yard box after a tremendous run from Dan Pybus had created the opening.
Saints, with 19-year-old wing-back Jay Henderson arguably the best performer on the pitch, missed chances to make their evening far more comfortable.
Main was unable to repeat his earlier accuracy with a header he sent over the bar before the lively Kiltie saw a shot deflected wide.
In the end, they rode their luck in stoppage time when defender Charles Dunne appeared fortunate to escape claims for a penalty against him for handball.
St Mirren (3-5-2): Alnwick, Fraser, Shaughnessy, Dunne; Henderson, McGrath (MacPherson 62), Power, Kiltie (Erhahon 62), Tanser (McAllister 73); Main (Erwin 62), Brophy (Dennis 62). Subs not used: Lyness, Tait, Flynn, Reid, Finlayson.
Dunfermline (3-5-2): Williams, Comrie, Watson, Graham; Macdonald, Allan, Pybus, Thomas (Wighton 62), Edwards; O’Hara, Todorov. Subs not used: Mehmet, Gaspuitis, Fenton, Todd.