'Angeball' is Celtic at their thrilling best and this is just the beginning - Tony Haggerty

"No, catastrophic to me means the end. This is far from the end. You are suggesting this is a club falling apart and our season is finished, I don't see it that way."

These were the words of new Celtic boss Ange Postecoglou when his side was knocked out of the Champions League by Danish outfit FC Midtjylland just over four weeks ago.

Postecoglou was firing back at a BBC reporter who claimed Celtic's exit from the Champions League was "catastrophic".

The Australian hinted then that his Celtic journey was just starting. He was also adamant then that the players and the faithful had yet to see 'Angeball' at work.

'Angeball' for those who don't know is a football ideology.

According to the man himself: "My goal is to have this club playing attacking football that's going to excite every one of you."

When 'Angeball' works it is aesthetically pleasing to the eye. When it doesn't it is going to give the Celtic supporter's heart failure this season. Tonight was a case in point.

This was Ange's biggest test to date of his Celtic managerial reign as Celtic faced a quality Eredivisie side in AZ Alkmaar. The Aussie came through it but only just as nerves were totally shredded.

Celtic certainly excited in the AFAS Stadion in Alkmaar and despite a 2-1 defeat on the night, Ange's men somehow sealed a place in the Europa League group stages courtesy of a 3-2 aggregate win but not before putting their supporters through the emotional wringer.

Celtic claimed a real scalp here but they had to do it the hard way with 'Angeball' pros and cons laid bare for all to see.

READ MORE: AZ Alkmaar 2 Celtic 1: Celtic try their best to blow it, but dig it out to make group stages

Goals by Kyogo Furuhashi and James Forrest had put Celtic firmly in the driving seat after last week's play-off round first leg in Paradise. A further goal by Kyogo - his seventh in eight games - in just three minutes had Celtic 3-0 up in the tie and in total dreamland.

The goal was pure 'Angeball' as Anthony Ralston sent Liel Abada scampering down the right with a defence-splitting pass and the Israeli winger's accurate centre was smashed home by Kyogo Furuhashi.

It was the green machine in full effect but the joy didn't last long.

By 26 minutes the picture had completely changed with Celtic the architects of their own downfall.

Joe Hart fresh air swiped a through ball which allowed Zakaria Abouklahl a walk-in goal just two minutes after Celtic had taken the lead and then Swedish international Carl Starfelt scored a crazy own goal when he inexplicably sliced a clearance into his own net.

AZ had been handed the initiative in the tie as well as a lifeline back into the competition as the Dutchmen took a 2-1 lead at the break.

READ MORE: Detailed Celtic match ratings as Anthony Ralston produces defensive heroics in AZ Alkmaar battle

'Angeball' was being tested to the full at this point and Celtic were struggling to get a foothold in the game. Australian midfielder Rogic was hooked on the hour mark in favour of Odsonne Edouard as Postecoglou tried to gain some territory.

The team were in much better shape after the switch as the manager adapted his tactics and style to the circumstances of the match.

Needs must and all that as Celtic were desperately holding onto the slenderest of advantages but they saw it through and the Europa League group stages now await.

Lisbon Lion Bertie Auld was dropped from the Celtic squad that famously beat Rangers 7-1 in the League Cup final in 1957. A reporter broke the news of the score and then asked him his thoughts to which Auld reputedly quipped: "It's a tragedy son...a marvellous tragedy."

For better or worse 'Angeball' has now officially been unleashed on Scottish and European football. From a disappointing Champions League exit to Europa League group stage qualification glory. It's been a massive turnaround for the 55-year-old in the space of just four weeks.

The contrast in mood and confidence could not be starker. Strap yourself in for one hell of a rollercoaster ride of a season. In the wonderful words of Auld, there could well be another "marvellous tragedy" in the making.

Marvellous for Ange, Celtic and their supporters. A tragedy for their opponents both at home and abroad. It most certainly isn't catastrophic or indeed the end.

In fact, it is merely the beginning.