Of the last seven games Celtic have played against Rangers, Sunday’s may have been the most bruising.

It wasn’t the defeat in isolation that would have been so difficult to stomach but the sense of deflation after so much hope in the build-up to the game that enveloped the club and its support. How wounding it transpires to be can only come down to Celtic and how they now react.

Cuffing Dundee and Hearts on the back of an inauspicious start fed a narrative that they were back on solid ground after the chaos of last season. The manner of the reaction to going out of the Champions League at the first hurdle and then dropping points at Tynecastle was enough to fuel a belief that they were battle-ready to take Rangers’ championship crown.

In a week in which they have lost twice in four days, one result significantly more damaging than the other, Sunday’s game was a sobering reminder that any rebirth does not come easily.

Indeed, Celtic will need to buck the odds now. Overwhelmingly the stats point to first blood in the Glasgow derby fixture as a fairly accurate barometer of title success; only five times in the last 32 seasons has there been a turnaround after emerging on the losing side from the first derby. Neil Lennon's 2011-12 team were the last to do it after a 4-2 defeat on the opening day.

Martin O’Neill wore the phrase thin in his opening season at Celtic, but the Ibrox side are the benchmark.  And it is only by bringing a level of consistency to their campaign that Celtic will find a way to eat into their territory.

Getting into Rangers’ psyche might be the bigger challenge; the longer it goes without a win in the fixture, the deeper the corrosion of belief going into games.

A 25-point gap between the teams might not have been reflective of the talent and ability of both squads last season but it showed the difference in organisation.

Ironically, Celtic’s loose threads were pulled apart entirely after the January defeat this year but there was a sense they were more dominant in that game than they were on Sunday.

Still, there is no indication that Sunday’s game will send Celtic into the same kind of freefall if the evidence of Postecoglou’s early era is to be interpreted.  Much of that comes down to the fact that there has been a clear buy-in of the Greek-Australian’s philosophy and mantra from fans and players alike.

There was an honesty in the reaction to the game from Postecoglou too as he accepted Kyogo Furuhashi would have been more effective playing through the middle for the entirety of the game.

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It was a decision that may not have been questioned had Odsonne Edouard met the Japan international's cutback with a clean shot rather than the inside of his heel in the opening period. All ifs and buts and maybes but ultimately there was not a huge amount between the teams.

Celtic’s biggest gripe might be that too many of their big players just didn’t have a big performance in them on Sunday.

Kyogo was far more threatening after Edouard had gone off, although there was a brief lesson in psychology after he opted to take a shot rather than square to Ryan Christie at the edge of the six-yard box; a minute later he opted to pass (and give the ball away) when he would have been better having a shot himself.

Among the reasons for the sense of expectation ahead of the trip across the city was the goals that Celtic have scored with some abandon in recent games. Of all the issues they have had since Postecoglou took over, scoring goals hasn’t been one of them.

Keeping them out has been another story. But when chances are passed up and there’s a vulnerability defensively– especially at set-pieces – there is always going to be a danger.

Where Celtic go from here now will be interesting. The defeat wasn’t the hiding they were on the back of last May but there is still work to be done.

Much, too, will be dependent on what business is conducted before the window closes with those going out as telling as just who might come in.

At this stage of the window as it heads into its final hours there is always a feeling that any pressing business is long done.

Christopher Jullien is due to return next month which ought to lend some steel and experience to the backline and there is no question that Celtic will be better for inclusion.

The challenge now, though, is to ensure that there is an immediate reaction to a significant moment of adversity.