Twelve months on from seeing their grip on Scottish football released by Rangers, Celtic are back on top ahead of a season-defining month for both sides of the Glasgow divide.
Transformed by the impact of Australian manager Ange Postecoglou, the Hoops have a three-point lead atop the Scottish Premiership ahead of Sunday's trip to Ibrox.
That is the first of three Old Firm clashes in the coming weeks with a Scottish Cup semi-final and a final league meeting of the season to come at Celtic Park.
Few saw a tightly fought title race coming when Postecoglou inherited a club in crisis in June.
Rangers had not only stopped Celtic's quest for a historic 10th consecutive league title, but were a juggernaut under Steven Gerrard as they went unbeaten throughout an entire league season to win it by 25 points.
As well as needing a new manager, Celtic also lost their long-serving captain Scott Brown and chief executive Peter Lawwell.
Postecoglou was not even the club's first choice as a prolonged and ultimately unsuccessful courting of now Newcastle boss Eddie Howe delayed the naming of a new manager.
The 56-year-old is revered in his homeland and well-respected in Japan from his three years in charge of Yokohama Marinos.
But he was met with a wave of scepticism over his credentials to oversee the overhaul Celtic needed.
Those doubts were not eased by three defeats in his first six league games, alongside an early exit from the Champions League qualifiers.
Recruitment has been key to Celtic's revival.
A total of 17 players have arrived during Postecoglou's first two transfer windows with precious few failures.
"I wanted to make sure the players fitted the ideology of the team I wanted us to be," said Postecoglou.
"You can't have square pegs in round holes. It's not just about getting talented footballers, it's about getting people who fit into my football."
His knowledge of the Japanese market has unearthed gems at bargain prices in Kyogo Furuhashi, Daizen Maeda and Reo Hatate.
But the net has been cast far and wide in the search for talent within the limited budget of Scottish football with signings from clubs in Israel, Ireland, Poland, Portugal, the Netherlands, Russia and the lower leagues of English football.
Any critics have since been silenced by a 31-match unbeaten run in domestic football.
"At the start it was all trouble, now it is all treble," Postecoglou added on the possibility of adding the Premiership and Scottish Cup to the League Cup won in December.
Victory at Ibrox would give the green-and-white half of Glasgow a commanding six-point lead with six games to play.
Yet, Rangers are also on course for what could be the greatest season in their 150-year history.
The Blues have recovered from losing Gerrard mid-season to Aston Villa to make the Europa League quarter-finals under Giovanni van Bronckhorst.
The prize for whichever side ends the season as champions is even more significant this season with the winners set to gain direct entry to the lucrative Champions League group stages.
That is thanks in large part to Rangers' European runs in recent seasons, but it Celtic who are in pole position to cash in thanks to Postecoglou's transformation.
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