Callum McGregor has been in with the bricks at Parkhead for nearly a decade so it’s hardly a surprise Celtic’s foundations look slightly shaky on the rare occasions he’s not around.

Which is why Stiliyan Petrov is convinced Hoops boss Ange Postecoglou is right to put the skipper right at the heart of his huge rebuilding mission.

McGregor missed out in the recent defeats to Real Betis and Livingston at the weekend with a hamstring problem and he might be forced to sit out Thursday’s Premier Sports Cup clash with Raith Rovers as well.

Petrov believes Celts can cope with the tie without their captain – but they need to hang on to him for the long term.

Postecoglou has kicked off new contract talks with the 28-year-old despite his current deal not up until 2024 amid constant talk of interest from Down South.

The manager sees McGregor as being a key part of his Parkhead revolution and Petrov believes it’s even more crucial to keep hold of the midfielder when there sweeping changes going on around him.

The former Hoops star said: “Callum has been instrumental at Celtic – and not just this season. We’ve seen how much of a miss he is when he’s not there.

“He has really matured as a player, you can see he leads the boys in the right way since he took over from Scott Brown as captain.

“He is a huge miss because he’s also one of the players who makes a difference in the big games.

“You can understand why Ange wants him to sign a new contract. Everyone wants to keep their best players –and he is one of the top guys.

“I really hope they can keep him for the long term.”

Petrov spent seven seasons at Celtic before his £6m move to Aston Villa but he isn’t too worried about McGregor heading in the same direction.

He said: “I know there has been talk about England for a while but at this moment I think he understands his responsibility to lead this Celtic team.

“The club are going through a transition and they need someone who has been here a long time and understands the club.

“Callum is taking this role very seriously and I hope it continues.”

Petrov insisted the 30-year-old needs time to build up to full fitness.

He said: “It’s very difficult for any player coming in who hasn’t played in a long time. You need to be at full strength to it’s been hard for him to hit the ground running.

“It’s going to take him time to build his fitness. We know he’s a good player. He’s played a lot of games in the top league in England, so we know he’s got it.

“But in football these days you have to run. It’s difficult if you are not match fit, but I’m sure the team behind Ange are working hard to get him up to speed.”

Stiliyan Petrov is campaigning against fraud

It’s not just McCarthy who needs time. Petrov isn’t surprised Celtic have been inconsistent as Postecoglou has been forced to reconstruct the entire squad on the hoof.

The Bulgarian international admitted he was struggled to get to grips with the Scottish game when he first arrived in 1999 and it’s the same with the current crop who have lost three on the bounce away from Parkhead.

Petrov said: “I got a shock when I came here, especially just how tough it could be away from home. When teams play against Celtic and Rangers, their performances go up 100 percent.

“They raise their game and fight for every single second on the pitch.

“I found it really difficult at first. It wasn’t just me either. We have seen lots of players coming from England or abroad and finding it difficult to adapt.

“It took time for me to adapt and it will be the same for these new players.

“Don’t forget, when I first came in I played with a very experienced team. I was surrounded by characters, international players who’d played at high levels.

“This is a brand new team with a lot of young players.

“When I played I had people around me telling me what to do and pushing me on.

“This is a young, inexperienced team that will take time to gel. They have played well at times but they are inconsistent. I think we have to expect it.

“There was a lot happening last season with Neil Lennon leaving and everyone knew the club would have to go through a transition.

“I think they missed the time when they had to do that and they’ve then had to do it very quickly with the manager and the new players.

“It’s going to take time for them to be more consistent.”

Celtic have lost all three away games this season and Petrov admitted it’s a curse they’ll need to conquer.

He said: “It’s a concern because psychologically players will be going in to away games under pressure now.

“But this is a transition period for Celtic with the new manager and so many new players, they are just trying to find their feet.

“The manager is also dealing with so many injuries to key players, and it makes it difficult to win games.

“Postecoglou has a lot to contend with, but what I like about him is he’s quite calm and he takes things as it comes.

“He knows his challenges but when he gets his important players coming back I think you’ll see a different Celtic.”

Stiliyan Petrov was speaking at The John Hartson Foundation Golf Day at Turnberry. The Hartson Foundation supports various cancer charities around the UK.