After being trounced by Legia Warsaw in the last round, but then being reprieved by Uefa following a Polish farce, some Celtic fans were still rubbing their eyes in disbelief that their team still had a chance of Champions League football.
Well, Maribor, a competent team from a modest football country, put an end to all that. Following last week's 1-1 first-leg, Celtic's 1-0 loss on Tuesday night was a dreadful spectacle for their supporters.
Ronny Deila, a new coach under relentless scrutiny at Celtic, must once more bear a heavy responsibility. His team's play on the night was ragged and bereft in the opening half, and only better without being outstanding after the break.
Deila had a golden opportunity, against all the odds, to steer Celtic into the £20 million jackpot of Europe's elite club competition. Instead, his plans crumbled against opponents of little star-status.
Where does this leave Deila and Celtic? What does it tell us about this coach and his methods, even this early in his Celtic career?
Celtic will now play in that ugly duckling called the Europa League this season. Ironically, a season in that competition - or even out of Europe completely - need not be so harmful to the club, as heinous as this will sound to Celtic supporters.
In just such circumstances Neil Lennon grew as a Celtic manager in seasons 2010-11 and 2011-12, when the European dimension was lost to the club. Financially, of course, this Maribor setback is a horrible blow.
Other things…it does not look good for Kris Commons' Celtic future. He was omitted from the start yet again by Deila against Maribor, and the only reason for this appears to be a clash of football principles between the two men.
There can be no doubting the quality that Commons has given Celtic since being signed by Neil Lennon in January 2011. Barring the odd dip, most Celtic supporters would say the 30 year old former Scotland international has been one of the club's best players in recent memory.
Deila, however, is having none of it. With his new, more demanding fitness regimen at Celtic, something between coach and player appears to have broken down. If there was one game which cried out for Commons to start for Celtic, it was this second-leg, yet the single-minded Deila declined the chance.
Just four days short of his 31st birthday, you could argue that Celtic have seen the best of Commons' career, and that his worth to the club is now diminishing with every passing month.
Commons' contract at Celtic expires next summer, just as he is reaching the age of 32. Given the type of player he is - a creative hub but not a high-tempo, energetic force - it may be that Deila envisages his reconstructed Celtic team minus this player.
None of that, however, explains why the player we have known these past three seasons could not have aided Celtic prior to arriving as a half-time substitute against Maribor.
Deila in these early furlongs is remarkably unmoved and determined. Most managers are, of course, but this Norwegian is particularly unflinching.
The past - in terms of a club's tradition or a player's reputation - appears to mean nothing to him. Deila wants to establish his own particular football culture at Celtic, and hell mend anyone who gets in his way.
Commons appears to have been a victim of this. So, too, Leigh Griffiths. And the flipside is that Callum McGregor, a player scarcely six weeks into his Celtic career, is valued and lauded by Deila, and effectively fast-tracked by his coach into the Scotland squad.
Equally, Deila happily ignores the fact that Jo Inge Berget was lampooned as a useless cast-off at Cardiff City, bringing the player to Glasgow, convinced by the knowledge that he knew a different, talented player from his time in Norway.
For any admirer of Deila, all this is well and good, and maybe even admirable. But his first task is to make Celtic win, and he has just failed again at that.
No-one knows this early how the Deila story is going to unfold in Glasgow. But this week, and this Maribor defeat, is a decided black mark against the Norwegian.