O’Neill was drafted in after Brendan Rodgers resigned on Monday with his team behind Heart of Midlothian in the league table, having missed out on Champions League football, and amid protests against the Celtic board over a disappointing summer transfer window.

“This is a big game for us,” O’Neill said. “Really, don’t disguise that at all. It’s a semi-final, it’s a big match for us.

“Any Celtic-Rangers game is a big game, but particularly given the circumstances of the recent days, if not weeks, absolutely.”

In his first spell, O’Neill won 16 of his 27 Old Firm fixtures, drawing three and losing eight.

However, there was just one victory from his four previous Hampden meetings with Rangers and there was just one League Cup success over his initial five-year stint at Celtic Park.

Asked about his derby memories, O’Neill recalled: “Just a nervousness for about 72 hours before and then, if you got the result, a great relief.”

When asked if he felt different this time around, he said: “Absolutely not. No, no, worse.”

O’Neill recalled that his first derby came after “five or six games” in charge, while Sunday arrives after just one this time – Wednesday’s 4-0 league win over Falkirk.

“I learned a great deal at the Falkirk game, which was great for us – a restoration of confidence,” he said. “So we’ll go into this game with that confidence and that’s the most important thing.

“But even if I was here a month or something, it would be really hard to gauge exactly what the players can do.”

Danny Rohl, half O’Neill’s age, will be in the opposite dugout in only his fourth game as Rangers head coach.

“I’ve heard a lot of good things and I think I said this even before I got this job,” O’Neill added.

“I think a lot of the players at Sheffield Wednesday were very complimentary about him.

“That was a big win for them there at Easter Road [1-0 against Hibernian]. So they’ll be going to the game with plenty of confidence themselves.”