Celtic’s Champions League hopes have gone up in smoke in one of the most remarkable European collapses in the club’s recent history.

Holding a 4-0 aggregate lead over LASK, Martin O’Neill’s side somehow surrendered their advantage in Austria before eventually losing the tie 5-4 after extra time.

It was a night that Celtic simply won’t want to remember.

O’Neill was brutally honest afterwards, accepting responsibility for the collapse.

“I’m responsible for this one. Without a doubt.”

The Celtic boss admitted the result was a major disappointment and acknowledged that his side are still a long way from being the finished article.

And the consequences stretch far beyond European disappointment.

Champions League qualification would have delivered a huge financial boost to Celtic, as well as making the club a far more attractive proposition in the transfer market.

O’Neill admitted that the absence of Champions League football could now affect Celtic’s ability to bring players to Parkhead.

“Financially, for prestige, but we have to pick ourselves up. That’s my responsibility again to do that.”

For Celtic captain Callum McGregor, there were no excuses either.

The midfielder admitted Celtic were too passive and looked scared to take control of the game.

“We got what we deserved. We were passive all night.”

McGregor also placed responsibility firmly on the players, insisting there could be no excuses after surrendering such a commanding advantage.

Former Celtic captain Scott Brown believes LASK simply wanted it more, while Neil Lennon described Celtic as looking exhausted and fragile in the key battles.

And that may be the biggest concern for O’Neill.

Celtic didn’t simply lose a football match. They lost a four-goal advantage in a game that appeared almost impossible to throw away.

Now comes the reaction.

The league campaign continues, the transfer window is still open, and O’Neill has to somehow lift a squad that has suffered a potentially defining European setback.

Celtic have been here before.

The question now is whether they can show the reaction their captain demanded.

Because after a collapse like this, the response could define their season.