There were two changes to the Aberdeen side that was well beaten at Easter Road last weekend, both enforced with Anthony Stewart having departed on loan to MK Dons and Liam Scales being suspended. In for immediate debuts in central defence came Mattie Pollock and Angus MacDonald, with Graeme Shinnie taking the captain's armband for Barry Robson's side. Dilan Markanday and Alfie Bavidge were among the subs.
There was just one change to the St Mirren side that won 1-0 at Motherwell on Saturday with Ethan Erhahon, having departed for Lincoln City, being replaced by Keanu Baccus.
The Dons won a corner on two minutes, a long ball forward from Matty Kennedy causing confusion in the St Mirren penalty area. As it was cleared, Aberdeen won a free-kick 30 yards out, on the right. Ross McCrorie got on the end of Jonny Hayes' ball in but planted his header into the goalkeeper's hands.
On five minutes, McCrorie was on the charge down the right. Dunne came across to block him and McCrorie raised his arm to keep his balance. McCrorie's arm caught Dunne in the face as a consequence and St Mirren were given a free-kick when it was Dunne who had first initiated the foul. VAR then took over and having looked at the monitor, the referee produced a red card for McCrorie. A debatable decision.
MacDonald was in the book on 13 minutes for a late challenge on Kiltie as he chased down the left. Thankfully, the free-kick came to nothing. It was a very scrappy opening to things after the red card, neither side really hitting their stride early on.
St Mirren were nearly in front on 25 minutes, a terrific cross into the box from Strain causing havoc, Pollock doing well to come across to get a block on Greive's shot from a dozen yards. Four minutes later, Ylber Ramadani took a stamp on the foot from O'Hara that required the physio to carry out some repair work.
Kennedy had Aberdeen's first shot in anger, running across the top of the box before pulling his effort wide of the target. Shinnie was floored after 35 minutes Dunne was booked. There was a couple of minutes of afters that followed, Ramadani and Greive booked for dissent in the aftermath as players squared up to one another. Ramadani took his frustration out on the ball seconds later, blasting it over the bar from 25 yards.
Main should have had the visitors in front on 38 minutes, O'Hara pulling the ball back through the six yard box, Main at full stretch somehow poking it wide of the target from the middle of the goal.
Leighton Clarkson tried to produce something miraculous on 41 minutes, firing the ball goalwards from the left touchline, 35 yards out, Carson off his line and desperately back-pedalling to tip the ball over the bar at full stretch.
Another good bit of defending from Pollock kept things level five minutes into added time a strong block as Greive was in position to shoot from six yards, the last real action of the half.
Gallagher came on for St Mirren at the break, Dunne making way. The visitors kept Aberdeen penned into their own territory in the early stages without really creating anything.
Shinnie was penalised for a dubious looking handball decision on 57 minutes at the by-line - it looked more as if the ball had struck his chest and gone behind for a corner. Strain drove in a vicious free-kick to the near post where Main got away from his marker and produced a clever glancing header to bullet the ball just inside the post for 1-0.
Main was in the mood now, a 20 yarder blocked well by MacDonald but the rebound fell nicely for O'Hara who fired a skimming shot just over the bar. Main got in behind again on 63, firing off a drive at goal from 12 yards that MacDonald did well to block wide. Pollock was then booked for a foul on Greive in the build up.
Lewis had to produce a very good save on 67 minutes, St Mirren's sharp passing working space for Baccus on the edge of the box. The Australian international got off a powerful drive that Lewis did well to palm over the bar.
It was nearly 2-0 on 70 minutes, Tanser crossing for Kiltie whose header thumped back into play off the bar. Hayes got a good block on Greive's shot from the rebound before Shinnie tidied up to put the ball behind. Greive took a knock in the midst of it and was then replaced by Watt.
Duk was the likeliest outlet for Aberdeen and on 72 minutes, he bundled his way down the left, into the box, in between three players before Fraser gave him a nudge to give the Dons a penalty and a lifeline. Miovski sent Carson the wrong way and rolled the ball into the bottom corner. All square again. Tanser then came off, Small on in his place.
On 81, Main had St Mirren back in front and to be fair to him, it was a superb finish. Baccus played the ball into him, back to goal and 14 yards out. One touch to control, he swivelled to hit it on the turn and buried the ball just inside the far post. Two minutes later, Duk and Clarkson were replaced by Marley Watkins and Dilan Markanday.
Lewis produced another sharp save on 89 minutes, Strain coming in at the back post and making a good connection with an O'Hara cross, Lewis doing well to palm the ball behind. Kiltie was replaced by Flynn as we edged into added time.
From the corner, Gallagher got a header to the ball six yards out. Hayes cleared it off the line, Watt tapping in from an offside position. VAR then checked whether the ball had gone over the line or not and decided it had - it was hard to tell without goalline technology.