Martin O'Neill has urged Celtic to demonstrate genuine character when they host Falkirk in the Scottish Premiership on Saturday, just days after one of the most painful results in recent club history.

The Hoops had appeared to have their Champions League play-off tie against LASK firmly in hand — leading 3-0 from the first leg in Glasgow, with Callum McGregor's deflected strike in the 21st minute extending that advantage on Austrian soil. What followed was a staggering collapse. LASK clawed back to win 5-4 on aggregate after extra-time, ending Celtic's hopes of Champions League football and dropping them into the Europa League.

O'Neill takes responsibility

The 74-year-old manager was candid about his own role in the defeat, admitting the manner of the capitulation weighed heavily on him. "To let it slip in the manner in which we did, that is my responsibility," he said.

O'Neill, who first managed Celtic between 2000 and 2005 before returning to lead them to the Scottish Premiership title and Scottish Cup last season, warned that the club's supporters would demand an immediate response.

"I've known this from my time at this football club — you're always one game away from a crisis, and that's the case."

He acknowledged Saturday's match against Falkirk would test Celtic's mental resilience, predicting a nervous atmosphere at Celtic Park if things go wrong early. "There'll be moments in the game tomorrow — misplaced passes, allowing Falkirk in, shots at goal and maybe even going a goal behind — where the crowd are going to get really restless," he said. "So we have to fight that."

O'Neill drew on memories of previous Celtic squads that included Henrik Larsson, Neil Lennon, and Paul Lambert to underline that the pressure of wearing the Hoops has never changed. "I wouldn't expect it to," he added. "We can't live on laurels for the rest of our time."

A tough Europa League draw

Celtic's drop into the Europa League brought its own challenges, with the draw handing them away fixtures against Benfica, Union SG, Omonia, and Torreense, and home ties against Marseille, Ferencvaros, Celta Vigo, and Besiktas.

O'Neill conceded the group represented formidable opposition. "I've got the list here in my pocket and Marseille and Benfica — I never read any further after that," he said. He acknowledged he had not yet fully processed Tuesday's exit but tried to find a positive. "It's something to look forward to. Some really big games there."

McGregor, who has been absent from training with a stomach bug, is expected to be available for the Falkirk fixture, according to O'Neill. The Celtic boss was clear-eyed about where his club stands: last season's triumphs belong to the past, and rebuilding trust with the supporters begins now.