Football managers will tell you that no player is indispensable. Some, though, are undoubtedly more dispensable than others.

When Celtic captain Callum McGregor suffered a knee injury during his team’s Champions League defeat to RB Leipzig in Germany last month, there was a widespread concern among the club’s support - and perhaps even the management team – that his leadership qualities would prove hugely difficult to replace. Never mind his abilities as a footballer.

When he is fit to return to the fold, he will of course be welcomed back into the starting XI with open arms, but the chasm his absence left in the Celtic team has been bridged in large part by the understated influence of Cameron Carter-Vickers.

The central defender has not only taken on the armband during McGregor’s layoff, but has taken on the responsibility of leading Ange Postecoglou’s group of players on the field, guiding them through difficult moments such as the late rally by Motherwell on Wednesday night that briefly threatened to deny Celtic a crucial win.

His form has also led to a call-up to the USA squad for the World Cup in Qatar, an announcement which came during the post-match debrief at Fir Park during the week and one that was met with great joy by his teammates, with David Turnbull summing up the feelings of the Celtic squad towards the gentle giant at the heart of their defence.

“I’m delighted for him,” Turnbull said.

“I thought he would have been picked, he’s been a mainstay in our team. You see how well he has done, and since he has had the captain’s armband I think he has taken it to another level.

“He’s a rock at the back, and hopefully he can go there and make a good impact.

“[He was reliable] last season as well. Ever since he has come in he has been very reliable, played most games, and he’s been solid for us.

“We’ve got a lot of big characters in the changing room when Cal’s not there. He’s still chipping in with wee bits before games and after games, but Cameron has done brilliant to step in. It’s a tough thing to do and he’s handled it well.

“Cal is maybe a wee bit more vocal before games or whatever, but sometimes it’s not about that.

“The way he carries himself on the pitch is an example to everyone else.”

The appreciation of Carter-Vickers from his attacking teammates in particular is in part fuelled by the insurance he provides them as they look to cause havoc at the other end of the field. It isn’t lost on any of them that the job of a centre-back in Postecoglou’s gameplan is one of the most demanding on the field.

“Everybody acknowledges what they do,” Turnbull said.

“Sometimes they don’t get the headlines that other boys get, but whatever partnership has been there this season has been great.”

The steadying influence of Carter-Vickers undoubtedly helped settle his teammates as Motherwell pulled a late goal back in Celtic’s 2-1 win on Wednesday night, with the fact they got over the line on a night they were below their best ultimately more important than how they managed it.

Turnbull knows from Celtic’s own experiences during last season’s title win that they can’t always be on the top of their game and blowing the opposition away, and that when they aren’t, they still have to find a way to win.

“That’s what has to happen if we aren’t dominating games like on Wednesday night,” he said.

“Teams are going to throw everything at us, so it’s about grinding out results when you are not playing well.

“That’s the sign of a good team I think, and we are doing well at the moment. It’s just about continuing the run.

“I don’t think you can go through a full season without teams testing you and challenging you.

“You get a new challenge every week, and coming back [to Fir Park] we knew what we were going to face after playing them a few weeks ago.

“They put up a great fight, and as the manager said, it is about grinding through these games and getting a positive result.”

It is an attitude that has taken Celtic seven points clear at the top of the table heading into the final game before the break for the World Cup, a lead they are trying their best to pay no heed to.

The Celtic players faced a similar deficit to Rangers around this time of the season during the last campaign, giving them a healthy dose of perspective now that the roles have been reversed, and reminding Turnbull that the fat lady has yet to even begin warming up her vocal cords.

“We know nothing is guaranteed,” he said. “It’s just about taking each game as it comes.

“We’ve not looked at the table too much, in fact I don’t think we’ll look at it all until the end of the season, that’s when it matters.

“It’s just about knuckling down and getting the results we have been getting so far.”