Despite Peter Weatherson's late double giving the scoreline a hint of respectability, the reality was that, Ton faced an SPL side who were superior in every department.
Big-name signings such as Steven Thompson and Gary Teale - both of whom were playing for Scotland in the not-too-distant past - were particularly prominent as their side cruised to a sixth consecutive Renfrewshire Cup win.
Yet, when the match began, there was little to suggest that this was the way things would turn out as the Ton players emerged fired up and desperate to make an early impression.
With just 25 seconds gone, Marc Smyth steamed into an early tackle which would certainly earn him a booking next week at Stranraer.
The hosts began dictating play with a fluid passing game which ensured proceedings would unfold almost exclusively in Morton's half of the field.
Teale was particularly prominent, and it was he who, in the 20th minute, burst into the box and fed Thompson with a neat flicked pass, which the former Rangers striker lashed across goal into the far corner to open the scoring.
Thompson grabbed his second just three minutes later when he darted ahead of his marker to head home Paul McGowan's inviting near-post cross.
St Mirren remained in total control for the rest of the first half, but failed to manufacture another real scoring opportunity as they steadily took their foot off the gas.
Things went from bad to worse for Morton at half-time when Andy Graham was withdrawn due to a broken cheekbone suffered in a head collision with Jeroen Tesselaar.
However, Ton made an encouraging start to the second half, with Paul Di Giacomo winning a free-kick on the edge of the box.
Peter MacDonald took the kick but sent a poor effort high over the crossbar in what would be his final contribution before he was subsequently replaced by Andy Jackson.
This change and the introductions of Darren McGeouch and Weatherson, in particular, would prove to be the catalyst for the late rally which saw Ton salvage some respectability. But before then, they would first hit rock bottom by conceding two further goals.
In the 55th minute, Thompson turned provider, easily holding off the attentions of Ross Forsyth before flicking the ball out to Steven Thompson, who made no mistake from 12 yards.
The travelling support's pain was compounded in the 69th minute when former favourite McGowan, who spent the 2006/07 season on loan at Cappielow, collected Paul McQuade's pass and breezed inside Smyth before expertly curling home.
With 10 minutes left, Ton were 4-0 behind and staring down the barrel of their highest Renfrewshire derby reverse since losing 5-1 at Love Street in 1994.
But Weatherson at least ensured that Ton would not suffer that ignominy by slamming home a powerful free-kick from 25 yards in the 81st minute.
He followed that up with another sensational strike five minutes later when he strode on to a Di Giacomo pass and fired a thunderous first-time drive past Saints keeper Craig Samson.