• READ MORE: Ryan Christie savouring every moment of career turnaround at Celtic

One of the key turning points in Stuart Armstrong’s career can be traced back to a day in October 2016. The 23rd of October to be precise.

With less than 30 minutes left on the clock, Celtic were drawing 0-0 with rivals Rangers in the Betfred Cup semi-final at Hampden Park. The board went up at the side of the pitch. Nir Bitton was ushered from the field and on in his place went Armstrong.

Ryan Christie won November's player of the year for his performances for Celtic. Picture: SNS/Craig Foy

By that point in what was Brendan Rodgers’ first season the former Dundee United player’s game time had varied. Yet, with his positive driving runs from the centre of midfield, Celtic were able to turn the screw, increase the pressure and ultimately emerge victorious.

Armstrong didn’t have a direct hand in the goal but his cameo was an important one. He started 17 of the next 18 games for Celtic and became a key player during the double treble success, earning a move to the Premier League.

Two years on from that day in 2016, Ryan Christie was summoned from the bench at BT Murrayfield as Celtic were tied 0-0 with Hearts in the Betfred Cup semi-final.

The 23-year-old had played just 292 minutes up until that point in the campaign. Yet, it was a surprise he had been playing at all. Having spent the last season and a half on loan at Aberdeen there was a firm belief that he would end up at Pittodrie permanently. Dons boss Derek McInnes had even kept his preferred No.22 free.

Ryan Christie was the matchwinner in the Betfred Cup final. Picture: SNS/Alan Harvey

If Celtic had managed to get the transfer of John McGinn from Hibs over the line before losing out to Aston Villa, the expectation was that the Highlander’s future at Celtic would have ended.

Unlike Armstrong two years ago, Christie was brought on at half-time, replacing the injured Olivier Ntcham in front of more than 61,000 fans at the home of Scottish Rugby.

Christie’s influence was much more discernible. He foraged and flourished from the centre of the pitch. It was he who was brought down for the penalty which was converted by Scott Sinclair to open the scoring. It was then his shot which was spilled by Hearts goalkeeper Zdenek Zlamal to allow James Forrest to double the lead.

Christie would provide the coup de grâce, running onto a loose ball at the edge of the box and placing a shot into the top corner to seal a Betfred Cup final place.

The player, the management team, the Celtic fans should all look back on those 45 minutes in the west end of Edinburgh as the making of Christie as a Celtic player. He has started every game since, scoring five goals and providing a crucial assist in the Europa League win over RB Leipzig, not to forget the effect he’s had in a Scotland jersey.

The transformation has been as quick as it has been impressive. There is a certain serendipity to the way he and his Scotland roommate, fellow Highlander and friend Armstrong have both blossomed following substitute appearances in League Cup semi-finals.

For Christie, injuries and a poor transfer window presented him with his chance and he has grasped it with both hands, owing to the player’s mentality. Speak to those who have had dealings with him or know him well and they will like mention a polite, nice and well-mannered human being.

But fortunately, in a football sense, he has had certain other qualities ingrained in him. There is a tenacity to the way he plays, an edge, while his bellicose nature comes to the fore on the pitch. Despite being a creative, ball-playing midfielder he is capable of handling himself, playing with aggression and putting his foot in - just ask McInnes who fumed that the player hadn’t been sent off during Celtic’s recent Betfred Cup success.

It is this attitude which has won Celtic fans over. Not only does he look to play positively, trying to progress play forward at any opportunity; out of possession he runs and battles and grafts, putting the effort in.

It is an approach which has been drummed into him via his dad Charlie, a former Celtic player. In a recent discussion with the Official Scotland Podcast, he spoke of his dad being his biggest critic, when he was coming through the academy at Inverness CT and even still now. Not only has it grounded the player but instilled a desire to be better.

Now he can no longer be referred to as Charlie’s son.

That was confirmed the moment he spotted a gap in the Aberdeen defence on Sunday. Aberdeen’s aggressive man-marking approach saw Andrew Considine follow Odsonne Edouard out of defence. The player who reacted the quickest was Christie, running off Shinnie. He made Dedryck Boyata’s decision for him, the Belgian dropping the ball over the Dons defence.

Christie took an excellent touch only for his first effort to be repelled by Joe Lewis. But, as he so often is, he was the sharpest to react, steering the ball into the roof of the net.

It isn’t a one-off. Three days later he provided a similar burst to provoke a pass from Kieran Tierney before putting Celtic ahead at Motherwell. In October he stormed the Dundee box. One second he was behind the ball supporting play, the next he was running past four opponents to score.

Then there was that second Scotland goal against Israel. As a long ball went up to Steven Fletcher, Christie was already on his bike: bursting through the Israel backline, like Yuri Gargarin penetrating the top layer of the stratosphere in 1961. Two excellent touches and the ball was at the feet of James Forrest to fire Scotland ahead.

Intelligent players anticipate. Unintelligent players react.

It was clear early in the season that Celtic were missing those devastating runs that Armstrong provided from midfield. That verticality, that anarchy which is so crucial to a team like Celtic who dominate possession with opponents sitting behind the ball and stifling play. When play is slow and ponderous these players are capable of going from first to fifth gear and ramping up the tempo. They make team-mate’s life a whole lot easier, providing both options and solutions with their runs.

It was something which McGinn would have provided. But more importantly it is something Christie is providing.

Tellingly, when Rodgers made seven changes from the Betfred Cup winning team for the trip to Motherwell, Christie not only retained his place but also his position. Olivier Ntcham was fielded on the left.

He has played himself into a position where he is now undroppable and deserved his November player of the month award.

And, what’s more, there is still plenty to come. Christie has replaced the energy, the runs of Armstrong, but he perhaps has a higher ceiling than the Southampton man. He is more of a Rodgers player. His technical and creative skills are more developed than Armstrong’s were at his age.

It has to be noted that it is early days in his Celtic career, despite signing back in 2015. But Christie has solved a problem in Rodgers’ midfield and now appears to be making serious tracks to becoming a key individual at Parkhead.

The startling similarities between the rise of Ryan Christie and Stuart Armstrong at Celtic