But while the star played a key role in his side's win, which came in a 4-2 spot-kick victory after extra-time finished 2-2, Saints gaffer Danny Lennon stressed that all his players deserved the fullest of praise.
"We worked very hard," he insisted. "Although there were tired legs out there, the players didn't stop believing and didn't give up.
"This is a great night for St Mirren football club."
Ryan Fraser, Aberdeen's man-of-the-moment, was given the rest he was promised by Dons boss Craig Brown and was replaced by Jonny Hayes.
Josh Magennis was brought in at right back with Isaac Osbourne moved into the midfield, while the Buddies made three changes from the side which lost to Dundee United at the weekend; Graham Carey, Jon Robertson and Lewis Guy making way for Dougie Imrie, Gary Teale and Sam Parkin.
And it was the big striker's back-post opportunism that gave the visitors the lead in the sixth minute as Jamie Langfield pushed Steven Thompson's header on to the bar, with the Parkin on hand to tap home.
Aberdeen, seeking a 13th game without defeat, responded with a series of attacks and when Clark Robertson sent a high ball into the Saints' area in the 22nd minute, Scott Vernon saw Samson well off his line and cleverly headed the ball over his head and into the net.
Following the break, a more solid-looking Saints emerged and deservedly regained the lead on 69 minutes, Kenny McLean rifling an unstoppable drive from 15 yards home beyond a stranded Langfield.
When Fraser replaced Vernon with just 12 minutes remaining, it brought a new verve to the Dons. In addition, Magennis was offered another chance to show his worth as a striker and his move from right-back was to prove inspired as the home side hauled themselves back into the game for a second time.
With referee Crawford Allan glancing at his watch, the Northern Ireland international stuck out a foot as Smith's 92nd-minute shot came across the Saints' penalty area and the touch was enough to deflect the ball past Samson and to put the tie beyond the regulation 90.
But after several scares in extra-time, McLean, Teale, Jim Goodwin and David van Zanten held their nerve for Saints as Stephen Hughes' missed kick and Samson's heroics against Smith proved enough to send the Super Saints on the march to Hampden.