Celtic suffered a stunning Champions League play-off collapse as LASK overturned a 3-0 first-leg deficit to win 5-4 after extra time and sent the Scottish champions crashing into the Europa League.
In one of the worst nights in Celtic's European history, the Hoops were up 4-0 on aggregate after Callum McGregor extended their 3-0 first-leg advantage early on in Austria.
Asked if it was the worst he's felt on the touchline, Celtic boss Martin O'Neill said: "Without a doubt. Naturally it took me a long time to get over the UEFA Cup final in 2003, but this was majorly disappointing."
Despite wobbling after goals from Moses Usor, Robert Ljubicic and a Samuel Adeniran stunner, Celtic were minutes from booking a place in Thursday's League phase draw before second-half substitute Florian Flecker headed home a 90th-minute equaliser to force extra time.
Full of all the energy and desire that Celtic whimpered at the sight of, the momentum belonged to the Austrian champions. Adeniran struck from range again in the 109th minute to put LASK in front on aggregate for the first time.
He very nearly added salt to Celtic's wounds when he stepped up for a penalty moments later, after Reo Hatate fouled Krystof Danek deep, but Viljami Sinisalo kept the spot-kick out to give his side a lifeline.
It was a lifeline that went begging as the full-time whistle confirmed Celtic would miss out on the Champions League for the second consecutive season. Last season they were eliminated on penalties at this stage by Kairat Almaty.
This year's failure, given the context of a four-goal aggregate lead, will be an even harder blow.
Once again the Hoops will be involved in the Europa League league-phase draw on Friday.
20: LASK CHANCES! The first falls to Mbuyamba in the area, who can't quite match the flight of the ball to send it goalwards. Any touch on that and Lask would have had a goal. The second has Sinisalo worried, as it strikes the post.
21: GOAL! It's a smart, smart low strike from McGregor but it takes a nick off Andrade and flies past Jungwirth in the LASK goal.
32: GOAL! IT'S A GIFT! Celtic punished for complacent play at the back. Nygren passes a ball back into no man's land, putting it on a plate for Usor to stroke past Sinisalo.
48: GOAL! LASK LEAD! Lask are beginning to believe. Ljubicic beats Sinisalo from range with a superb low strike from the edge of the area.
58: GOAL! WHAT A FINISH!!! That is simply superb technique. No chance Sinisalo was getting anywhere near that. The LASK striker is teed up outside the box and curls home.
90: GOAL! LASK MAKE IT FOUR TO SEND IT TO EXTRA TIME! Sinisalo does brilliantly to deny Joao Victor Tornich initially, but he can do nothing about the rebound as Florian Flecker heads home to make it 4-4 on aggregate!
108: GOAL! Nightmare stuff for Celtic as Adeniran strikes from range again. LASK now lead on aggregate.
114: FROM BAD TO WORSE! Hatate brings down Danek in the box and gives away a penalty! However, the effort is saved.
Celtic boss Martin O'Neill speaking with Amazon Prime:
"We should've been out of sight by half-time. We missed two great opportunities and then we gave them a lifeline right before half-time and then another one just after it. They came roaring back. That's my team, that's my responsibility.
"At half-time I thought we were still well in command of the game. Just after, they score and then momentum goes in their direction. It's hard to stem it when they're chasing the game and we can't get out for 10 minutes.
"These are tough games. This might have been a qualification game but it felt like a Champions League game. That doesn't matter. Talking about the squad is for another day.
"It's a massive disappointment. We're playing in the Europa League but that's no consolation this evening. There was a feel-good factor and that's a massive disappointment tonight."
Celtic's Callum McGregor speaking with Amazon Prime:
"We got what we deserved. I thought we were passive all night. We actually looked scared to go and win the game.
"To be honest, I don't think we were that good in the first leg either and we kind of got away with it. But then you're up 3-0 and think you have a chance. When you play like that, you can't have any excuse whatsoever.
"We have to suck it up. We apologise to the supporters and to the club because there's no way we should lose that game. Now we have to see what character we have.
"You can't lose the game by such a big margin and look for excuses elsewhere. This is where we see what people are made of in terms of what we achieve this season."
Your Site News' Adam Binnie:
"The big one for this is finances. Everyone will talk about the prestige and that's a big thing for Martin O'Neill - but what the club will be concerned about are the financial implications.
"£40m is the estimated total you get for qualification into the league phase of the Champions League. That's split into various parts.
"There's the UEFA Value Pillar which can add anywhere between £14m and £16m and you get at least £16m for automatic qualification no matter what happens.
"There could also be £10m added to that in gate receipts in ticket sales if Celtic were to sell out all four home matches.
"The finances are pretty drastic which has a knock-on effect. Celtic were planning on splashing the cash once again. They've spent £30m already, so where does this leave them?"
LJJ: "Absolutely embarrassing for Celtic, maybe Europa League is the level for them since they get into the CL with ease every year but don't make an impact when actually in it. Maybe that's their level, but I don't think they deserve Europe at all after what I've just witnessed!"
Jonny: "Celtic got what they deserved. They didn't exactly play well last week and were lucky to come away with three goals and decided to park the bus, just not good enough."
Reinaldo7: "Don't know whether to laugh or cry. Worse than last year against Kairat. Strange choices for subs tonight. Hang your heads in shame boys, they weren't that special but made us look ordinary. More work needed if we are to succeed in Europe."
Stevo: "I think this was worse than Kairat. Yes, it's not ideal losing on penalties to them, but to be 4-0 up and throw that all away, that's impressively shocking!"
jcluk: "No more LASK chances for Celtic. They were hapless, hopeless and humiliated. Can see them struggling domestically too this season."
Celtic will play in the Europa League this season. The Europa League league phase draw - involving Bournemouth, Sunderland and Crystal Palace - takes place at 12pm UK time on Friday
