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At 10:20pm on Wednesday, Ange Postecoglou walked slowly out of the tunnel at Tannadice, made his way out on to the pitch, took his phone from his pocket and made a video call.
To who, we don't know, but we can guess it was to someone close to him. There he was, in a stadium that had all but emptied, having this private moment on possibly the greatest day of his managerial life. It was a lovely scene.
He stayed there for 10 minutes then returned to the happy chaos of Celtic's inner sanctum. The 12th person to manage the club to a league title. When a reporter quoted that stat to him earlier on, he replied that it was "fairly overwhelming" and that it had taken "every ounce" of him to get there. There was a bit of emotion. You could see and hear what it all meant to him.
What was noticeable in the celebrations at full-time, and for the many jubilant minutes that followed, was Postecoglou's contentment to stay in the background. Occasionally, he was in the front line with his players, but for the most part, he hung back, letting them drink in the glory as if he was mere facilitator rather than great redeemer.
The job the Australian has done is akin to a magician's touch. He inherited a side that was beset by doubt and made all its problems disappear. Rangers' title, won by 25 points, has vanished in a puff of smoke.
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Everything is under control at Celtic again, where before the place was thrawn. Postecoglou, an immigrant at the age of five when his family moved from Greece to Australia, has revitalised a club set up for immigrants. Less than a year ago, few in this country had even heard of him. Now he has ensured that nobody will ever forget him.
Their hard-fought draw against an excellent Dundee United - themselves bound for Europe next season - puts Celtic on 90 points, a total that eclipses the haul in five of their nine-in-a-row seasons. If they beat Motherwell at home on Saturday, this term would go to joint third on that list.
Even before the trip to Tannadice, their goals scored tally was ahead of five of their nine-in-a-row campaigns.
That's some going for a side that was largely recruited in two windows in what was one of the biggest rebuilds in the club's history. Postecoglou's signings have accounted for 73% of Celtic's league goals. Liel Abada, Kyogo Furuhashi, Jota and Georgios Giakoumakis have scored 60 between them in all competitions.
A few weeks back, Postecoglou said this season was just phase one of what he wants to do at Celtic. He followed up more by saying that he has only scratched the surface of what he aims to achieve and he reiterated those words on Wednesday.
We await his next moves. The suspicion is that we won't have to wait long. Postecoglou doesn't like to let the grass grow under his feet. He has built a team that, you fancy, will only get better once it gets a proper pre-season together and once some of its more tired players get a long-deserved rest.
He'll recruit with the Champions League in mind. Quality over quantity, you suspect. His team played 14 games in Europe last season and won only five, conceding 28 goals in the process.
They're better now, but to make a mark on Europe, they're going to have to be more defensively robust and more physical in midfield. Challenges, challenges. They're in a position of strength to meet them.
In the next phase, as he has called it, he could do with chipping away some peripheral figures to make way for some stellar operators.
Boli Bolingoli, Albian Ajeti and Vasilis Barkas are still taking a serious wage; money that could be used to lure players who contribute more to the cause. These three have 10 league starts combined this season. Mikey Johnston has five, Ismaila Soro and James McCarthy six. The desperately unlucky Christopher Jullien, now 29, has played 16 minutes since December 2020.
That's hundreds of thousands of pounds a month and millions a year on bit-part - or no-part - players. If they're going to achieve something in Europe they could do with upgrades in these departments, particularly in the battleground of central midfield, where a top-notch holding player is required.
Postecoglou says he knows precisely the type of player he wants to fit the system he deploys. That clarity of thought was part of the reason why he hit the bullseye so often in the transfer market in his two windows.
Mohanad Jeahze, a Sweden-born Iraq international left-back from Hammarby, appears to be on his way to Glasgow as part of the next wave. High-energy, attack-minded, the Postecoglou identikit footballer.
Improving his team and his squad will be the sole focus come season's end on Saturday and he'll do it while knowing there's considerable growth potential in what he already has. As a collective, they're still bedding in.
Abada, Matt O'Riley and David Turnbull are 20, 21 and 22. Jota and Anthony Ralston are 23. Reo Hatate, Daizen Maeda, Greg Taylor and Cameron Carter-Vickers are 24. Locking down the permanent signings of Jota and Carter-Vickers will be an important part of the forward planning.
The Celtic manager couldn't have asked for much more from Kyogo, Hatate and Maeda. The former has missed practically half the season through injury but has scored 10 Premiership goals. How many might he be on had he not been absent for 18 league games?
Hatate hasn't lit it up of late, which is hardly a surprise. In the last 15 months, he's played J-League, Japan Super Cup, Emperor's Cup, AFC Champions League, Olympic Games, international friendlies, Scottish Premiership, Scottish Cup and Europa Conference League. He's played 67 games, criss-crossing the globe on a number of occasions in between.
You could say the same for Maeda. He's played 65 for clubs and country since the start of last year. He's scarcely had time to draw breath, not that he looks weary. What might he be like when he has a summer off?
Two of the by-products of winning the Premiership are money and time. Celtic will rake in £30m-plus in European loot and will also be spared a murderous qualifying schedule, a run of games that would have played merry hell with their early season.
In the last three years alone, they have had to travel to Denmark, Czech Republic, Netherlands, Latvia, Bosnia, Estonia, Romania and Sweden in pursuit of group-stage football. They already have it now. That's a seismic change in their world.
Postecoglou has created a champion team, but it's the thought of what he might have in store in the time ahead that must be truly exhilarating for Celtic supporters.
They celebrated a title on Wednesday and will do it all over again on Saturday, but part of their euphoria must lay in the belief that their manager is only getting going. So much already done, so much more he wants to do.
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