Several parallels can be drawn between Stuart Armstrong and Ryan Christie.

Both were brought to Celtic in the same era under Ronny Deila. Both had to wait sustained periods of time before making an impact from the bench in a big game and becoming integral parts of the team. Both heavily contributed with goals from central midfield during a couple of seasons bringing great success, and the pair are very close friends off the park.

They only featured together nine times though, and Armstrong's form under Brendan Rodgers limited Christie's opportunities and rendered him initially surplus to the Northern Irishman's requirements, meaning some tutelage from Derek McInnes up north was in order. Christie was a star pupil, growing in confidence, quality and stature up at Pittodrie during his near 18-month spell in red.

The summer Christie sealed his second loan to Pittodrie saw a mini-saga unfold with Celtic's golden boy Armstrong. It was 2017 and the graceful midfielder was basking in the glory of a 17-goal season that kick-started when he netted the fifth in the opening derby of the season. Armstrong didn't look back and was nominated for PFA Player of the Year as Rodgers' first season climaxed with a Scottish Cup final win over Christie's Aberdeen. Armstrong scored the equaliser, to cancel out an opener from Johnny Hayes, who would then join Celtic weeks later with Christie temporarily going the other way to sweeten the deal for the Irishman, who had previously worked with Rodgers at Reading. Football's a small place, really, isn't it?

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Armstrong had a year remaining on his contract, which allowed a "will he, won't he" storyline to develop surrounding the signing of an extension to his deal, which he eventually did on vastly improved terms until summer 2019, scaring off those pesky vultures in Southampton and other admirers like Brighton and West Brom, for the time being.

The Saints inevitably came back 12 months later and took Armstrong, by now a fully-fledged member of the Scotland squad, for £7m and everyone was a winner, but Celtic needed a new goalscoring midfielder to fill the gaping void created by Armstrong's departure.

Perhaps this is the most glaring difference in how Celtic careers panned out for Christie and Armstrong, who was last week plucked with glee from the UK transfer market's reduced aisle by Bournemouth, with his imminently expiring contract cutting about 75% off his genuine value.

At the same time as Armstrong's camp negotiated his new deal, Christie was starting the final year of his contract and bracing for a move away from Celtic, either to Aberdeen on a permanent basis or Hibs as part of a deal to secure John McGinn. Celtic hesitated, McGinn moved to Villa and the door remained slightly ajar for Christie. He burst it down in October in the League cup semi-final against Hearts, replacing the injured Olivier Ntcham at the interval when the score was 0-0 and proving to be the decisive factor by winning a penalty, having a shot spilt by Bobby Zlamal for James Forrest to tap home and then scoring a gem from the edge of the box.

In the three years after signing until that point, Christie had only made 23 appearances for Celtic with 15 of them coming from the bench. He was a peripheral player suddenly launched into the spotlight. Confidence coursed through his body with Brendan Rodgers lauding him as "sensational" and rewarding him with an improved three-year contract.

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Five goals in the next six league games, a glorious assist for Odsonne Edouard's winner against RB Leipzig, the decisive goal in the League Cup final against Aberdeen and international recognition all followed. Like Armstrong, he seized his opportunity and didn't look back. The dam had been burst and suddenly Christie's career was moving at 100mph.

In his ensuing 151 appearances, he didn't play more than a third of them in one single position. Christie's versatility and goal threat from all angles instantly made him valuable across the front three and he consistently produced from all of them. He played 49 times as an attacking midfielder, scoring and assisting 16 teams while in that berth. He was tasked with cutting in from the right on 30 occasions, scoring eight times and assisting five while doing so. His contribution from the left was lethal too; in 19 appearances from there, he scored six and assisted 8. On the rare occasion he was deployed as a striker, he still scored twice and set up another. Simply, Christie turned up for Celtic. A lot.

What might sting though, after a difficult season under Neil Lennon during which consistency was lumpy from time to time, is Christie was perhaps given the perfect manager at the wrong time.

With his contract running out in the January window, there were concerns about how he'd approach the start of such a vital season for Celtic. Any fears were allayed instantly as he slotted into Postecoglou's system with ease, mostly on the left as Kyogo Furuhashi flourished through the middle. A goal against Jablonec and three assists in the league left supporters in little doubt he would be an important member of the squad even if he stayed until his contract ended in the new year. His fervent elation when Celtic got over the line against AZ Alkmaar and a 20-minute stint as captain against St Mirren a few weeks ago gave hope to the believers that maybe Christie wanted to be part of Postecoglou's project. The Aussie hadn't kept his desire to keep Christie a secret, saying after the 6-0 thrashing of Dundee on match-day two: "I don’t think I need to twist his arm. I’ve already said that if this doesn’t convince him, I don’t think anything can." An 18-month extension, on improved terms, before being sold next summer for a price reflective of his quality, would have been a nice compromise for everyone. Football is a short career though and the 26-year-old had already made his mind up.

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Christie's desire for a new experience may well cloud the clarity with which he is remembered by a number of Celtic supporters, especially considering his move is to the English Championship rather than the Premier League, a level befitting of his ability. Foreign clubs like Nice, Monaco and Sampdoria were allegedly circling as well as neighbouring sides Burnley and, in a stunning shock twist for a departing Celtic player, Southampton, but Christie actively chose The Cherries. Perhaps others wanted to wait until the January window rather than pay, but Bournemouth's short-term financial sacrifice will reward them in the long run.

The truth is, the English Championship is an extremely attractive proposition and a superb stepping stone for players looking to progress to an elite level. Christie was also allegedly on a contract not really reflective of his standing in the team, meaning his move down south will bring him a significant pay rise in a fiercely competitive league. I'd hedge my bets though that he's remembered fondly by Celtic supporters.

Christie took the goalscoring mantle from Armstrong. Over to you, David Turnbull.