For those who like their plot lines thick and brimming with intrigue, steering clear of Paisley last night seemed the judicious option. A Celtic side with the scent of the Treble in their nostrils facing a St Mirren outfit badly in danger of entering free-fall scarcely looked like a recipe for a Friday-night thriller. And yet, for all Ronny Deila’s side prevailed in the end, this scrap provided compelling evidence that they won’t simply be given a free ride towards a fourth successive title in the coming weeks. Celtic winger Kris Commons (right) has a shot on goal during the SPL match against St Mirren on Friday . St Mirren's Jim Goodwin slides in with a challenge on Celtic midfielder Stefan Johansen at St Mirren Park . St Mirren (4-4-2): Ridgers, Naismith, McAusland, Genev, Tesselaar, Goodwin, Dayton (Thompson 78), Mallan (Sonupe 77), McGinn, Sadlier (Morgan 73), Arquin . Subs not used: Kelly, Gow, Reilly, Wilks . Booked: Goodwin, Genev . Celtic (4-4-2): Gordon, Matthews (Ambrose Emuobo 65), Van Dijk, Denayer, Izaguirre, Brown, Johansen, Forrest, Commons (Mackay-Steven 72), Armstrong (Bitton 66), Stokes . Subs not used: Guidetti, Zaluska, Griffiths, McGregor . Scorers: Forrest 64 . Referee: Alan Muir . St Mirren may be at the bottom of the Premiership table and still four points from even a play-off spot but, on this showing, they aren’t out of it yet. They frustrated Celtic for the most part here, their energy and belief taking them so far — but not far enough. James Forrest was the man whose intervention broke Gary Teale’s heart with a second half tap-in while any realistic chance of an unlikely comeback was killed off when Stefan Johansen later converted from the penalty spot. Now eight points clear of Aberdeen, however, Deila’s misgivings about a far from perfect display will be tempered with a realisation that the title is edging ever closer to his grasp. The Celtic boss made four changes from the side which won the last of the four game-series with Dundee United before the international break. St Mirren goalkeeper Mark Ridgers (centre) comes out to punch the ball clear of the head of Jason Denayer . Commons (right) and Ste Mirren's John McGinn (left) tussle for the ball during the SPL match on Friday . St Mirren's Jason Naismtih (right) battles with Stuart Armstrong (left) during the SPL match in Paisley . Out went Efe Ambrose, Nir Bitton, Gary Mackay-Steven and John Guidetti with Adam Matthews, Anthony Stokes, Kris Commons and Forrest the beneficiaries. Surprisingly, given the poverty of his side’s display in the defeat to St Johnstone, Teale made only three alterations with Kieran Sadlier, Marc McAusland and Yoann Arquin restored to the side. St Mirren’s attempts to address the obvious quality gap with guts and industry bore early fruit. With next to no time on the ball, Celtic were unable to find their rhythm let alone a killer pass. Commons, typically, was the man who found the space others couldn’t in order to fashion the first chance. Dropping into a pocket of space behind the Saints defence, he gathered Scott Brown’s incisive pass then shaped as if to cross. His attempt to beat Mark Ridgers at his near post was audacious but unsuccessful as the goalkeeper turned the ball around the post. Now playing without the burden of international football, Commons looked better for the break. When Johansen picked him out 30 yards from goal, he glided away from three challenges before lashing a shot into the side-netting. Largely written off as relegation certainties after their last dire outing in Perth, no one could accuse St Mirren of not giving it their all as they sought to claim an unlikely bonus point to help their plight. Celtic's James Forrest (left) tussles for the ball with St Mirren's Jeroen Tesselaar (right) on Friday night . St Mirren' s Yoann Arquin (left) has a shot at goal but it is saved by Celtic goalkeeper Craig Gordon (centre) Celtic really ought to have taken the lead in 26 minutes. Stuart Armstrong had started the game with a couple of heavy touches but his pass to Commons was perfectly weighted. Commons took one touch to control and a second to blast the ball towards Ridgers’ goal. The keeper blocked smartly, though. St Mirren then finally worried Craig Gordon. Sadlier danced away from Matthews on the flank and found the space between Celtic’s central defenders where Stephen Mallan was lurking. His header floated towards the keeper’s top corner but never with the required velocity to beat him. Ridgers was earning his corn. When Commons turned provider for Forrest, the winger looked to have picked his spot in the bottom corner with a side-foot only for the keeper’s agility to leave the Celtic star with his head buried in his hands. It served to embolden the home side. Armstrong’s tackle on Sadlier inadvertently set up Arquin but the striker seemed spooked by the chance and fired weakly into Gordon’s arms. Deila isn’t renowned for endangering crockery collections at half-time in dressing rooms up and down the land but it can safely be assumed he had a few choice words for a Celtic side that been some way short of sparkling in the first period. Celtic manager Rory Deila (left) gives instructions to his captain Scott Brown (right) against St Mirren . Forrest slides on his knees to celebrate scoring Celtic's opening goal against St Mirren on Friday night . Armstrong’s dipping shot from 20 yards was a yard shy of changing the narrative of the night within 60 seconds of the restart before Stokes’ snap-shot was easily claimed by Ridgers. When Jeroen Tesselaar needlessly conceded a corner, he was grateful to the goalkeeper for punching Jason Denayer’s header off his line. Commons smashed the spoils low into the side-net. Mallan issued a timely reminder that St Mirren were still very much in the game with a strike that had Gordon scrambling. The Saints midfielder sprawled to the turf after a foot sprint with Brown on the counter-attack but ref Alan Muir wasn’t interested. Just as the Buddies looked to have the measure of the league leaders — so much so that Deila was looking to his bench — one moment of slackness cost them dear. Brown was the catalyst with a supreme pass in behind Tesselaar, taking the Dutchman out of the game and holding up perfectly for Matthews. Celtic midfielder Johansen slots home from the penalty spot to secure his side's 2-0 victory at St Mirren . The Welshman’s low cross was accurate and turned home with a flash of Forrest’s boot at the far post — his second goal in three games. With that, Matthews and Armstrong departed to be replaced by Bitton and Ambrose before Mackay-Steven came on for Commons. Saints, to their huge credit, stuck to their task with Jim Goodwin, who had been harshly booked in the first half, seemingly at the heart of everything. Some 11 minutes from time, the result was put beyond all reasonable doubt. Forrest’s shot did strike Viktor Genev on the arm but there seemed a case to be made in mitigation that it was not deliberate. The Bulgarian was booked for squabbling with Muir’s decision but the delay didn’t perturb Johansen who calmly sent Ridgers the wrong way from 12 yards.
Celtic extend their lead at the top of the Scottish Premiership table.
James Forrest scored the opener for the visitors before Stefan Johansen made sure of three points from the penalty spot.
St Mirren remain bottom of the league table with 21 points.