O’Neill has transformed the mood around Celtic Park since make a stunning returnMartin O'Neill and Callum McGregorMartin O’Neill and Callum McGregor(Image: PA)

Callum McGregor admits Martin O’Neill has completely transformed the mood at Celtic with his trademark positivity.

The Hoops skipper says the legendary boss has reignited the dressing room since his stunning return to the dugout.

Celtic had endured a worrying slump in Brendan Rodgers’ final few months, adding to the toxic atmosphere surrounding the club.

But O’Neill’s shock comeback has sparked a revival, with back-to-back wins over Falkirk and Rangers restoring belief among players and fans alike.

McGregor was left gutted by the nature of Rodgers’ exit but insists O’Neill has galvanised the champions after a turbulent campaign.

The captain said: “He’s been great. Someone with huge experience and has been around the block so many times. A really calm influence.

“He was exceptional. He asked for the intensity from the players and I think in the first-half, you could see.

“We pretty much won every duel, every first ball, every second ball. We were excellent. He was a big part of that. A real calm head.

“He asked us to go and play, believe in yourself and you’ll go and win the game. So he’s been excellent.

“You want to work with top, top managers and he’s someone who has been around the block a fair few times.

“His experience, he’s managed at such a high level. He’s come in and just pumped everyone full of confidence.

“The players feel good. They want to run, fight and that’s exactly what you need in this game. He’s been excellent since he’s come in.”

McGregor – who scored a screamer to give Celtic the lead at Hampden in extra-time – also heaped praise on the interim coaching staff of Shaun Maloney, Mark Fotheringham and Stephen McManus for guiding the squad through a traumatic week.

He said: “It’s a collective effort. It always has been, it always will be. The staff behind the manager have been so, so good this week.

“Just having that continuity of message, the training level, it’s all interconnected. The manager can’t do it on his own.

“He needs his backroom staff and it’s the same that players can’t do it on their own. We need everybody.

“So it’s a real collective effort and that’s something I’m super proud of in the past week.”

Celtic captain Callum McGregor is mobbed by team matesCeltic captain Callum McGregor is mobbed by team mates

Celtic will now play St Mirren in next month’s Hampden showpiece as they look to defend their trophy.

And McGregor reckons the priceless win over Rangers can be a major turning point in the season.

He admitted: “I think it was a big day. If you don’t win, it probably just heaps more pressure on what’s been a challenging start to the season.

“The slate was cleaned, the performance on Wednesday night was excellent and then to come and deliver on a big day today, it shows me how much talent and ambition is in that dressing room as well.”

Rookie strikers Johnny Kenny and Callum Osmand also announced themselves as Celtic players by netting in the 3-1 win.

Irish target man Kenny bagged a brace in the midweek thumping of Falkirk, while Welsh teen Osmand made his senior debut.

McGregor added: “It’s always an opportunity for every player when they come in. They are working so, so hard to develop to the level of the first-team boys.

“Johnny scored two during the week and you just know – I’ve been around football for a long time – I just knew that he would have an impact today.

“And he has taken himself to another level in terms of status now scoring against Rangers. So he’ll be brimming with confidence.

“The same with young Ozzy. He’s been working so, so hard in the time he’s been out of the squad. But he’s a player who trains so, so hard every day.

“He has a nice finish as well, so he’s one that’s just going to keep developing and strikers with confidence can go and conquer the world.”