It has been all about the numbers for Celtic this season.

But as they trudged into the dressing room at half-time, the only one at the forefront of the minds inside Celtic Park was the number 3.

Yet, it took a mere sixty seconds to turns this tie on its head as Celtic kept their Treble aspirations alive.

There had been that rare afternoon in the Celtic Park dressing room.

A team talk delivered to a trailing team, a team who had produced the most insipid opening 45 minutes of Brendan Rodgers’ regime.

Read more: Exclusive: Celtic striker Moussa Dembele says he's a better player this season than last year in England - thanks to Brendan Rodgers

Given the magnitude of the game – league blemishes will detract from the goal of creating a new record of unbeaten games but will not deviate from delivering a sixth successive title – as they look to secure a Treble for only the fourth time in their history, this game resulted in an anxiety that few would have predicted beforehand.

Yet, Celtic pulled themselves out of the more with a strong second period with the usual suspects shining brightly; Scott Sinclair most of all. Sinclair netted an exquisite effort to put Celtic ahead for the first time in the game, while Mikael Lustig got the goal that Celtic craved as they got a toehold back into the game.

From there on in, strikes from Moussa Dembele and Leigh Griffiths put the Parkhead side into a comfort zone that seemed far off the radar when they headed in for a half-time breather.

However, it was one of last season’s leading lights that helped to orchestrate the change with Leigh Griffiths, a second-half sub for Nir Bitton contributing to a sixty second turnaround that kept Celtic’s Treble aspiration alive.

It was the running of Griffiths as he chased a long ball and drew a foul from St Mirren’s Stelios Demetriou that provided the free-kick from which Celtic found the crucial leveller.

Read more: Exclusive: Celtic striker Moussa Dembele says he's a better player this season than last year in England - thanks to Brendan Rodgers

And where they had slept through an opening period that had allowed St Mirren to take a shock but deserved lead, they shook off their slumber to emerge into a second half full of the vim and vigour that has marked much of this season.

Rodgers rang the changes quickly with his substitutions quickly and effectively making their mark. First was Patrick Roberts who took over from Gary Mackay-Steven who toiled dreadfully throughout the opening half.

The former Tannadice winger took a hefty boot in the head as he went for a ball in the penalty box but even allowing for any subsequent staggering effects, his overall contribution had been poor as he lost his way repeatedly with the ball.

Roberts’ pace and trickery made a difference and when Griffiths took over from Nir Bitton 9 minutes after the restart, Celtic were quick to establish a firm grip of the game that had eluded them for the entirety of the first period.

Griffiths had a hand in the leveller as he chased the ball down the channel, drawing a foul from Stelios Demetriou. Roberts supplied the delivery into the box with Lustig getting a head to bundle the ball into net and puncture the optimism among St Mirren’s ranks.

Almost immediately prior to that Celtic had a massive slice of luck in keeping the scoreline down when Dembele cracked his own crossbar with an attempted clearance – and as the ball came down behind Craig Gordon; the keeper could only look with relief as the effort did not cross the line.

Celtic’s response was prompt. Off went Bitton, on went Griffiths and within a minute they were on top for the first time in the game.

Lustig netted, then Sinclair nailed Celtic’s progress with a second and the game was done. St Mirren knew it too as they sunk within themselves.

Read more: Exclusive: Celtic striker Moussa Dembele says he's a better player this season than last year in England - thanks to Brendan Rodgers

It was a far cry for the first half when they had flirted with causing a shock.

Jack Ross’ side had taken the lead as they capitalised on a Celtic defence that looked uncharacteristically sloppy.

Cameron Smith’s cross was knocked down by John Sutton and, with the Hoops defence static, Harry Davis, on-loan from Crewe was played onside by Dedryck Boyata and stole in at the back post to knock the ball into the net from close range.

It was not enough of a shock for Celtic to take note with St Mirren forcing Boyata to clear his lines and concede a corner shortly after as the Championship side, emboldened by their opener, went for another.

It said much about Celtic’s performance – and St Mirren’s tactics – that in that opening half hour the Saints keeper Billy O’Brien has just one save to make when he collected from a relatively tame effort from Stuart Armstrong after being teed up by Gary Mackay-Steven.

There was no real surprise that the changes were rung at the break – but what might have raised an eyebrow was just how different the second half performance was from the first 45.

It could have finished with Celtic bagging six with two goals chopped off for offside.

There were few complaints, though, as Celtic eased their way into the semi-finals of the William Hill Scottish Cup and within two games of winning a Treble.