Having lost all six of their previous league outings, the Paisley side saw their early- season sparkle fade as they plummeted to one point above the back-marking Dens Park outfit.
By contrast, after initially seeming like lambs to the slaughter after their unexpected elevation to Scotland's top flight following the "old co" Rangers' demise, Barry Smith's resurgent team have in recent weeks claimed victories over both Edinburgh sides and drawn at Motherwell. So the importance of this fine 3-1 win for St Mirren, restoring as it did the gap between the two sides to four points and putting a welcome full stop on their worst run under Danny Lennon, could be priceless.
Indeed the St Mirren manager's relief was self-evident. Lennon said: "I know you get the same three points no matter how the win comes. But we have been playing to a similar level and not getting our rewards so I am delighted we finally got the three points we merited.
"There was a real hunger to the players from the start and we handled everything that Dundee threw at us. Even when Dundee levelled we got a fantastic reaction and we could have had more. We have raised expectations and we are building solid foundations. I am delighted for the boys. Now we need to kick on."
Psychologically at least, there was plenty riding on the outcome and the game quickly developed into a full-blooded affair, but a moment of madness left Dundee with a numerical disadvantage.
With the match tied, Colin Nish showed his studs in a challenge on Paul Dummett in 27 minutes and referee Willie Collum unhesitatingly flourished his red card.
Four minutes later, the hosts made their advantage count. A delightfully weighted Kenny McLean pass found Lewis Guy just in behind the Dundee rearguard and he rounded Rab Douglas before attempting to slot the ball home only for it to be cleared off the line and Stevie Thompson was on hand to follow up with a point-blank finish to make it 1-0.
Then, right on the stroke of half-time, Paul McGinn's cheeky chip was brilliantly tipped on to the roof of the net by Douglas as the veteran keeper once again demonstrated a dexterity that mocked his advancing years.
The second period started as the first had finished, with Dundee remaining in the contest thanks to Douglas producing a stunning stop on Thompson's eight- yard header.
Then in 64 minutes the visitors found a way back when Nicky Riley's cutback was needlessly handled by Jim Goodwin and Ryan Conroy stroked the resulting penalty home with assurance.
St Mirren, though, were in no mood to relinquish this gilt-edged opportunity to put valuable points on the board and they regained the lead when Gary Teale's free-kick was headed in by Thompson in 72 minutes.
Four minutes before full-time Marc McAusland's pinpoint delivery picked out substitute Dougie Imrie, who smashed home his first goal for the Paisley men to finally kill off Tayside hopes.
Dundee manager Smith felt the game turned on Nish's dismissal. He said: "I felt it was harsh. I felt that we worked hard in the second half to get back in the game. That spirit exemplifies our team, we will just not give up. We have still along way to go, but we have come a long way."