Scorers: Aberdeen - Reynolds (45), Pawlett (51); St Mirren - Ball (57), McLean (86 pen)
Aberdeen were looking for a fourth successive home league win for the first time since Jimmy Calderwood was in charge six years ago and current manager Derek McInnes will find it hard to believe they didn’t get it as Kenny McLean’s 86th-minute penalty earned the visitors a precious point.
The Dons pounded St Mirren’s goal for long spells but inaccurate finishing and an inspired goalkeeping display by Marian Kello set up a barely believable denouement.
Only the winning margin should have been in doubt but St Mirren showed the sort of spirit needed if they are to avoid a season-long battle against relegation.
McInnes had indicated his clear intent to keep the goals coming at the end of an impressive home run by bringing back Niall McGinn after injury at the expense of Andrew Considine.
That meant Jonny Hayes returning to the left-back position, although once again he was more often occupied pushing foward in support of the wave of Aberdeen attacks.
In fact it was Hayes who forced Kello into the first of numerous saves that the St Mirren goalkeeper was called on to make as the home side pushed forward with verve from the off.
As early as the sixth minute Marc McAusland was forced to resort to illegal means to prevent David Goodwillie breaking clear from deep and earned a booking for his trouble.
The width, pace, movement and quality of Aberdeen’s link-up play was a severe test for the visitors’ defence with Hayes, McGinn and Willo Flood all going close early on.
Ironic then that the clearest chance in the opening stages came at the other end when Ashton Taylor was short with a passback that was intercepted by Gregg Wylde.
However, the former Rangers youngster lacked the composure to fully exploit the situation.
Jamie Langfield raced out to block but the Aberdeen goalkeeper had the crossbar to thank for denying McLean a goal in 20 minutes when the midfielder’s 25-yard effort fizzed beyond him.
Those were rare moments of anxiety for a side who threatened to score virtually every time they went forward, breaking against St Mirren’s wall of defenders from all angles. In 24 minutes McGinn swapped passes with Goodwillie only to see Kello produce a breathtaking save high to his left to push the Northern Ireland striker’s drive wide.
Adam Rooney then sent a free header from Barry Robson’s corner down into the ground and saw it rear up and over the crossbar before Kello produced a stunning save to thwart Goodwillie at point blank range.
McGinn had a swing and a miss right in front of goal when any connection with a sublime curling cross from Rooney would have broken the deadlock. An Aberdeen goal seemed inevitable and it duly arrived at the cruellest time possible for a team that had defended as if their lives depended on it throughout the first period.
St Mirren’s luck ran out with virtually the last kick of the half and after all the imaginative forward play it was captain Reynolds who delivered it.
McGinn swung in a corner from the left, Goodwillie attempted an outrageous backheel that confused several defenders and Reynolds took advantage to spin and hit his first league goal of the season.
It was the perfect way for the centre back to celebrate his inclusion in Gordon Strachan’s squad earlier in the day.
Peter Pawlett doubled the Dons’ lead six minutes after therestart, taking advantage of a lucky deflection off Rooney’s shoulder to clip a half volley past Kello from 12 yards.
If St Mirren were demoralised by that, then they had a funny way of showing it as right from the restart they hauled one back as Aberdeen’s defence switched off.
Wylde sped clear down the left hand side and played an inviting cross to the back post where Callum Ball arrived to clatter the ball into the unguarded goal.
Kello continued to produce a series of heroic saves to keep his team in the game but there was still a sense of surprise when Reynolds inexplicably handled a John McGinn cross in his own box with four minutes left.
McLean kept his nerve and while Langfield went the right way, the strength and accuracy of the spot-kick saw it nestle in the bottom right corner of the net and St Mirren celebrated as if they had won a cup.
Aberdeen: Langfield, Logan, Taylor, Reynolds, Hayes, Pawlett (Smith 79) , Flood, Robson, McGinn (Considine 69), Goodwillie, Rooney. Subs not used: Brown, Murray, Low, Monakana, Shankland.
St Mirren: Kello, Naismith, McAusland, Goodwin, Kelly, Reilly (Caldwell 77), McLean, McGinn, Wylde, Marwood, Ball. Subs not used: Wilks, Brown, Williams, Yaqub, Baird, Morgan