Martin O'Neill addresses Celtic return timelines for Kieran Tierney and Callum McGregor

Tierney joined skipper Callum McGregor on the sidelines but Celtic managed to prevail thanks to a penalty shootout victory, with Tomas Cvancara stroking home the winning kick to spark scenes of serious crowd disturbances in the stadium as fans from sides spilled onto the pitch.

O’Neill was caught up in the mayhem on the pitch at the end. “I just said well done to the team and I went into my own little room to cool down myself,” he said later. “My heart's beating at a rate that a 74-year-old's shouldn't be doing.”

The manager, who is expected to leave Celtic at the end of the season, can still lead his team to the Double before he exits. The Parkhead side have drawn St Mirren - who beat them in the League Cup final in December - in the semi-final.

Celtic are currently five points behind leaders Hearts. They host Motherwell, beaten 2-1 by Dundee on Saturday, next in a clash between second and third place. O'Neill was asked what victory at Ibrox might mean for the rest of the season.

“There's going to be twists and turns,” he said. “I went to Dundee yesterday with Shaun Maloney and Mark Fotheringham to watch the game. We've got Motherwell next, which will not be easy for us. So I honestly don't know.”

Celtic look set to be without the inspirational McGregor for a period of time. He has suffered a recurrence of the calf injury that troubled him last season.

“I think that (winning without McGregor) shouldn't be overlooked ,” he said. “He was feeling it in Aberdeen (on Wednesday). I think the medical team were saying it's something that was here last year and maybe has come back. So the best thing to do was just to take him out of it. Kieran Tierney was certainly not right to start in the game. He might have been able to have come on, I think, but I thought, well, who knows what might happen during the course of it.

“He might have been forced to go on after five minutes in the match and he wouldn't have lasted. So for us to miss two big players like that there and still come through, it was brilliant.”

He addressed the likely timeline for both absent players. “I'm hoping that he will be back for next week,” he said on Tierney. “Callum, we would just have to have a look. Before the game, when the two of them dropped out, it was a major loss. So for the players to compensate for that, it was brilliant.”

Although ‘keeper Kasper Schmeichel returned to full training on Friday it was Viljami Sinisalo who continued in goal. He looked assured. Schmeichel was not even in the squad. “I just asked him, could he command the six-yard box?" said O'Neill. "And he did that wonderfully well. And when it looked as if he might have been beaten, then somebody else got the block on for him. So I was really delighted with him.”

O’Neill hailed the composure of the penalty takers, with Celtic converting all four of their penalties on front of the Rangers fans in the Copland Road Stand. Reo Hatate was one of the those who scored having seen his kick saved by Rangers 'keeper Jack Butland seven days earlier. He eventually scored on the second rebound in the 2-2 draw in the league.

“Once I saw that Reo was down as one of the five penalty takers, I might have been a bit concerned,’ said O’Neill. “It didn't take him three attempts to put it in. He wanted to take the penalty.

“The most important thing, I think, about these things is that five of them wanted to take the penalties. So that's great. I must admit that they took them brilliantly. They were obviously under a lot of pressure to do it. So to step up and take that walk for a start…You can take penalties (in training), which we did, but you can't really – what shall I say – you just don't know what it's like until you step up and take the penalties. It was pleasing to see how well they did it.”