Trapattoni's biggest competitive defeat in his four years as Ireland boss
The air-tight defence that Ireland prides itself on leaked like a rusty bucket as fanciful dreams turned into a full on horror show with the fear of the task ahead now etched on faces all around Poznan.
Having conceded just three goals in their last 14 games before this clash, it took Giovanni Trapattoni's men 49 minutes to repeat the trick as they folded meekly under unrelenting counter-attacks from a Croatian side with one win in their last four games before this.
This was Trapattoni's biggest competitive defeat in his four years as Ireland boss, although his heaviest remains the 3-0 friendly loss to Australia back in August 2009. It was also the fifth time his team has conceded three goals in a game.
Reaction: The party will go on but will have hollow ring after Croatia defeat
The manner in which his players crumbled will be hard to stomach for the 73-year-old Italian who last night became the oldest manager at a European finals.
But then again, a defeat like this was always coming. Having managed to somehow survive unscathed in a litany of games they should have lost, a pasting like this was overdue. The timing was a bitch though.
Mario Mandzukic, twice, and Everton's Nikica Jelavic combined to render Sean St Ledger's first-half equaliser meaningless as Croatia punished casual defending as Slaven Bilic's men raced into pole position in Group C.
This was Ireland's first tournament defeat since the defeat to Holland at USA 94 and they have it all to do now to get out of this group. They always did. But the fact they were such a hard team to beat carried some weight going into the campaign.
Not any more. Ireland were stripped bare and, at this top level, exposed as the ordinary team they are.
Ireland's only saving grace was the 1-1 draw played out in Gdansk between Italy and Spain. Bottom of the table, yes. But not as far off the pace as they might have been.
That said, avoiding defeat in last night's game was of paramount importance as the no-longer 'Lucky General' Trapattoni sends his men into battle against Spain on Thursday and Italy next Monday needing results.
The only positive on a grim night was the manner in which Trapattoni's men got themselves back into the game after conceding so early on - and even that is clutching at straws.
With just 42 percent of possession in the first-half, it was no surprise the goal came via a set piece delivery from McGeady as St Ledger got the better of Vedran Corluka - a weak link in the Croatia defence last night who wasn't tested nearly as much as he should.
But thereafter the attack lacked bite with aimless and unimaginative balls forward to Robbie Keane and Kevin Doyle easily dealt with. Jon Walters and Shane Long added more urgency after the break, as did Cox out wide with McGeady hauled ashore.
They harried and hassled for the remainder as Ireland chased a game that always got away from them after the concession of a horrendous third minute goal that exposed Shay Given's lack of sharpness after his recent injury woes/
Darijo Srna's cross whilst under pressure from McGeady and Stephen Ward clipped off the latter's back and fell to Mandzukic who somehow stayed composed as he slipped to plant a header past Given who took an age to react.
Yet credit Ireland who got back on level terms 16 minutes later. Corluka bundled Doyle over on the touchline and McGeady's fizzing free was steered home off St Ledger's shoulder. It was reminiscent of his goal against Italy in the last World Cup campaign.
But Croatia were always a class apart. Luka Modric was not at his magical best, but he didn't need to me. Others around him like Srna, Mandzukic, Jelavic and Ivan Perisic, in particular, were top class. And Given was forced into a full save to keep out one stringing Perisic drive from distance.
The Ireland No 1 also kept out a Modric shot while team-mates queued up behind him with Perisic flashing wide in a dominant spell illustrated by the fact that striker Keane was defending deep in his own box.
All of this was building towards something. And sure enough Jelavic pounced two minutes before the break to puncture Irish belief once and for all.
Comical defending saw the ball pin-ball around the edge of the box with it deflecting off Ward - who endured a torrid night at times - and into the Everton striker's path who cooly slotted home past Given from close range.
Croatia's 227 passes completed to Ireland's 138 at the break told it's story. Ireland were getting the runaround as they so often do, but this time there was no fairytale ending.
Any remote chance of a second Iriash equaliser were ended four minutes into the second half when giant Wolfsburg striker Mandzukic powered home a header from a Perisic cross that clattered off the post and off Given's head.
The comical nature of the goal summed up Ireland's night.
Trapattoni's attacking substitutions added a new dimension but it was a futile exercise really, notwithstanding two Keith Andrews efforts late on and another from Richard Dunne which was saved by Stipe Pletikosa.
But all of that was too little, too late. Spain loom large on Thursday.