Celtic suffered a damaging and likely decisive Europa League knockout round play-off first-leg defeat to Stuttgart as Martin O'Neill's 1,000th match as a manager ended in disappointment.
Bilal El Khannouss' first-half double sandwiched Benjamin Nygren's cool finish put Stuttgart in control as they punished defensive fragility to leave the home side with a mountain to climb to progress.
Goalkeeper Kasper Schmeichel had a night to forget, looking at fault for the first and third goals as he tamely failed to stop Jamie Leweling's second-half strike that earned Stuttgart a commanding cushion.
A fine late fourth finish from Tiago Tomas ended Celtic's 10-game unbeaten run since Wilfried Nancy's exit and leaves them with little hope of progression.
Under O'Neill, Celtic had produced some memorable displays and results in this competition.
They struggled to hit those heights despite playing well at times and now travel for the return leg against a side who sit fourth in the Bundesliga needing to record a first-ever win in Germany.
O'Neill stated in the build up that this would be a very tough test. It proved that but, in truth, Celtic's biggest obstacle seemed themselves.
They looked comfortable until Schmeichel was short with a clearance. The ball found El Khannouss whose reversed strike seemed tame, but the goalkeeper looked very laboured as he failed to get down to save.
Stuttgart captain Atakan Karazor was equally accommodating shortly after as he gifted Celtic a lifeline when he passed straight to Nygren who did superbly to round the goalkeeper and tap home.
That was his 18th goal of the season - a spectacular return from the Swedish midfielder.
Just as the home crowd sensed that reprieve may inspire something, they were undone once more. A cross deflected kindly to El Khannouss all alone in the penalty area and he planted a header home.
It was all far too easy.
Not for the first time of late, O'Neill was left with a half-time rousing mission to get Celtic back on track.
There was a response, but again Schmeichel looked at fault when Lewling struck from outside the box.
A fourth was ruled out when Ermedin Demirovic lifted home but the video assistant referee (VAR) deemed him offside to Celtic's relief.
Nygren was close to reducing the margin as the home side performed well enough and ploughed on but they were caught out in injury time when Tomas ghosted in to loft home.
The damage was done in those defensive moments with no miracle under O'Neill on this occasion.
