It was 90 minutes which brought a near-perfect record against Rangers for Brendan Rodgers crashing down.
Not once in two-and-a-half years in charge at Celtic had the former manager tasted defeat to their arch rivals.
But in December that all changed when Steven Gerrard's pumped-up side put on their best display of the season in front of their own fans to seal a 1-0 win and draw level at the top of the Premiership with the champions.
The Hoops' insipid display was as much a surprise as the result. Rodgers' side looked leggy, out of ideas and out of shape.
And there was one key decision in the now departed Northern Irishman's team selection that baffled Celtic fans, not least former striker John Hartson.
The decision to replace Kieran Tierney at left back with Callum McGregor not only left the midfielder badly exposed in an alien position but also removed a vital cog from the Celtic midfield.
The fact Tierney was thought fit enough to take his place on the bench for the match only served to further the confusion over the decision.
Tierney is again struggling with injury leading up to Sunday's latest meeting of the rivals having missed out on the Scotland double header against Kazakhstan and San Marino.
His inclusion at Parkhead on Sunday is vital to Celtic's hopes, according to Hartson. But, even if the 21-year-old doesn't make it, Hartson reckons McGregor's inclusion in his natural midfield berth will be a boost from last time out.
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“Having Kieran Tierney back is key," Hartson said in his Evening Times column.
“Not only is he one of our best players and pivotal to what so much of the team does, it will also mean Callum McGregor starting in midfield and not at left-back.
"That's a decision which doesn’t make any more sense months later."
Hartson reckons Neil Lennon will be buzzing to get back into the Old Firm atmosphere after returning to replace Rodgers at Celtic Park last month.
And he reckons with his old team mate in charge, there will be little chance of a second defeat in a row.
A win or a draw will as good as cement 8-in-a-row. And Hartson said: "His message will be simple. Don’t let this happen again.
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"I know what it’s like to be in the dressing room. Scott Brown will be reminding his team what so-and-so was saying after the game, what was written in the newspapers or said on television.
"Brown didn’t have his best day – I did feel some of the criticism was over the top – and there were a few who wrote him off, with some believing that he was on his way to Australia.
"The captain, I am sure, will be a lot better this Sunday. Rangers will see the real Scott Brown at Parkhead."
