The journey to the Champions League is all about the figures.

But for Brendan Rodgers last night it was number crunching of a different kind that provided the headache after a moment of madness from Jozo Simunovic left Celtic looking at a major defensive issue for next week’s second UEFA Champions League qualifier against Rosenborg.

A late injury too for Moussa Dembele will also have been a cause for concern.

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This second leg against Alashkert came close to calling for a requirement of fingers and toes to keep count of the scoreline given how dominant Celtic were against the Armenians but the real problem for Rodgers will come next week with Simunovic suspended and Dedryck Boyata enjoying a holiday following his World Cup exertions.

Celtic were able to absorb the blow without noticing it too much last night but it could be a different story next week given the lack of options at centre-half.

It had all started so seamlessly too for Rodgers’ side who face a marathon qualification campaign if they are to replicate the group stage involvement that they have involved in each of Rodgers’ two seasons at the club.

There will be a disquieting unease at going into the next round, regardless of just how impressive they were in this opener, without an experienced centre half.

UEFA Champions League qualifiers are notoriously edgy affairs but with a three goal lead from the opening leg against Alashkert and a Dembele goal after just seven monutes of this return leg, there seemed little anxiety within Celtic Park.

Even after Simunovic had a rush of blood to the head that saw him handed a straight red – the Croatian defender apologising to the Celtic dug-out on his way off the field – there was little need for panic given the position the Parkhead side held.

With Celtic cruising and essentially going through their paces, Simunovic inexplicably raked a high boot down the back of Jefferson Reis de Jesus just inside Alashkert’s own half. There seemed to be a slight hesitation on the part of referee Horatiu Fesnic before he produced the red card, much to the shock of the defender.

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Goals followed on from Simunovic’s absence – Dembele added a second from the spot and James Forrest added another before the interval had come round – but it was not last night where his absence was going to be felt.

Celtic will host Rosenborg in Glasgow next Wednesday night after a stoppage time penalty from the Norwegian side enabled them to see off plucky Icelandic minnows Valur but they will do so with a familiar defensive problem weighing on their minds.

Simunovic’s suspension for the second qualifying round comes just as Boyata is sunning himself by the pool after a World Cup third place finish with Belgium, while Marvin Compper has rarely been sighted since heading into Glasgow last January.

The German defender has made a couple of pre-season appearances but has played just one competitive game for Celtic when he featured last term in a Scottish Cup tie against Morton.

It could mean that there is a recall for Cristian Gamboa or Mikael Lustig – also just back in training after being out in Russia – with Jack Hendry and Krsitoffer Ajer making up a central defence and Kieran Tierney slotting in on the left.

The other alternative could be Anthony Ralston coming into the back four. In any case, Rodgers now has a problem for next week that will dominate over his thinking as he approaches the next hurdle on the way to the group stages.

Having seen off Alashkert with ease, all should have been rosy in Celtic’s garden but defensive issues at this stage of the season seem to be becoming the norm for the Parkhead side.

In terms of the performance itself, Celtic were fluent, aggressive and ruthless.

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Dembele looks as though he has returned from the summer break in the mood to find the form of his inaugural season. The French forward carries genuine menace whenever he breaks forward and in these opening weeks of the season he has been complimented by the addition of Edouard.

Where Celtic seemed to stutter with Leigh Griffiths and Dembele in tandem, they are far more slick with the two Frenchman leading the attack.

Edouard’s movement was too much for Alashkert with Celtic’s third of the night coming after a 30-yard burst from the striker before he placed the ball into the feet of Forrest. The winger’s raking finish underlined another player who appears prepared to pick up where he left off.

Certainly, the early evidence provided by Celtic so far this term – and it is early days – is that they can raise the bar another notch.

Crucially, where they want to do that is in among Europe’s best for a third successive season.

The last thing Rodgers would have needed last night was a moment of carelessness that has the potential to carry serious ramifications.

By the time Edouard went off to be replaced by Scott Sinclair shortly after the hour mark he had done enough to earn not just the applause of the stadium but from his manager too.

No sooner had Edouard gone off than Dembele went down with an injury and Ryan Christie came on to take over.

By that stage the tie had been long been put to bed.

Rosenborg will pose a far greater test than Alashkert and will be expected to pose more questions. Craig Gordon had just one save to make last night but will expect the going to get a little tougher next week.