Martin O’Neill believes Celtic will try and behave like a Champions League club in the next five days despite missing out on the riches of the competition.

Four goals up on aggregate, Tuesday’s astonishing collapse against Austrian champions LASK came with the veteran still to finalise his squad for the season.

Despite signing four players, the club failed to seal deals for targets including Ermin Mahmic, Landon Emenalo, Niko Sigur and Gvidas Gineitis before the play-off.

O’Neill remains optimistic that prospective recruits will still be tempted by Europa League football — and feels the club intend investing significantly ahead of the window closing on Thursday.

‘I honestly think that is the club’s aim,’ said O’Neill. ‘We’ve brought in a couple of players that I think will do really fine for us. I’m hoping that there’s an opportunity before the transfer deadline to make the squad stronger, to make it better.

‘And to compete in European football, you need that.’

Martin O’Neill believes Celtic can still bring in top quality despite exiting the Champions League

Asked what positions he was looking to prioritise, O’Neill added: ‘You would be definitely looking for a left-back for [cover for] Kieran [Tierney], because Kieran’s not going to, with the greatest respect, play all the games at the end of the day.

‘You’d need probably need a really strong replacement for Arne Engels, a box-to-box midfield player.

‘We definitely just would need strengthening and that’s what we’re going to try and do.’

Meanwhile, O’Neill feels Celtic have been dealt a difficult hand as they bid to make an impact in the Europa League.

The Scottish champions have been handed home matches against Marseille, Celta Vigo, Besiktas and Ferencvaros.

They will also travel to play Benfica, Union Saint-Gilloise, Omonia and surprise Portuguese Cup winners Torreense.

O’Neill helped Celtic progress to the knockout round last season by accruing 11 points and he feels this year’s task will every bit as difficult.

O’Neill expects the club to source backup for Kieran Tierney before the transfer window closes

‘I probably still haven’t got over the game on Tuesday night, but it’s something to look forward to, I must admit,’ said O’Neill. ‘There are some really good games there.

‘I’ve got the list here in my pocket. I saw Benfica, I never read any further…’

O’Neill, who expects Callum McGregor to be available to face Falkirk today after missing training yesterday through illness, has challenged his players to show what they are made of.

‘I know it’s an overused word, but we have to show a lot of character,’ he added. ‘There’ll be moments in the game, misplaced passes, allowing Falkirk in, shots at goal, maybe even going a goal behind in the game where the crowd would want to get really restless.

‘Absolutely, so we have to fight that. But that’s always been the case. And do you know what? I wouldn’t expect it to. 

‘We can’t live on laurels for the rest of our time. Last season was just fantastic, great moments, but it’s gone.’