PERHAPS the only negative about playing for Celtic in Kieran Tierney’s eyes is that he can’t be on the pitch and in the stands at the same time. Few have embraced the supporter-turned-superstar dream more than the 20-year-old who remains perhaps the only footballer to have been fairly sanguine about being injured as it gave him the opportunity to watch the team in action just as he used to do as a boy growing up.

Tierney has been blessed with a maturity beyond his years and spoke respectfully and sensibly about it being “only half time in the tie” following last week’s 5-0 first leg play-off win over Astana that has all but sealed Celtic’s place in the Champions League group stage for a second successive season.

Ask him about the atmosphere and the fans, however, and his eyes light up with almost childlike enthusiasm. The return of the Green Brigade following a temporary ban helped elevate the noise level at Celtic Park before and during Wednesday night’s match to a near-deafening din, the sound backed by a banner – inoffensive this time – that depicted manager Brendan Rodgers, captain Scott Brown and Tierney all roaring in trademark fashion.

The slogan on it - “we’re not here to take part, we’re here to take over” - is a quote commonly attributed to Conor McGregor. When the UFC fighter the next day tweeted his appreciation of the whole scene, Tierney was quick to further spread his hero’s message. When you are a regular pick for your boyhood club and the fans make a banner featuring your likeness, you surely know you have made it.

“I was buzzing with the display,” he said. “It was class. I really enjoyed that. And the whole atmosphere was crazy. You can’t really prepare for the Celtic Park atmosphere. You think you know what it’s like but it still takes you by surprise. They go up a level every time.

“The noise the other night was great and that spurs us on as players. The fans are the 12th man and they are brilliant for us. And for the away team to hear 60,000 people singing like that, it must be hard for them.”

Little wonder the mood both on and off the pitch was one of celebration. This was meant to be one of the most difficult matches Celtic would face all season against a side they only narrowly defeated at home a year ago courtesy of an injury-time penalty. Twelve months on and Celtic, following a tight opening, were wiping the floor with them. By the end it began to look as if they might score with every shot.

No team has ever overturned a five-goal deficit in the Champions League qualifiers and Astana surely won’t be the first to achieve that on Tuesday night, even with their impressive home record. That Celtic have taken the potential peril of the return leg out of the equation by being so emphatic at home is surely a sign of how far they have progressed under Rodgers’ watch.

“A year is a long time,” Tierney said. “When the gaffer came in [last year] the qualifying rounds were just the start and we hadn’t worked long under each other. As a squad we have improved so much. Last year was great for us and now we have to achieve things this year, too.

“I think everyone is thinking with the one brain now. Last year we were just getting to grips with it. We were getting better as training went on. And a year down the line I think everyone can see how much we’ve improved as a team. We’re much better and fitter.”

On a personal level Tierney has undoubtedly come on leaps and bounds, too. There will be major English and European clubs monitoring his progress but he feels he still has further improvements inside him.

“I’ve come far but I’ve worked hard every day to achieve that,” he said. “The manager has shown great faith in me and that gives me confidence when I go out on the park.

“I feel that I’ve still got a lot to give and I’m working hard every day to try to get better. I’m nowhere near the perfect player. Far from it. I’m working hard on all my weaknesses and there are plenty of them.

“I’ve got a hard role now getting up and down the pitch all game but in training when you’re in that position you’re playing against top wingers and full-backs. It prepares you for games like these. Testing yourself against Scott Sinclair, James Forrest and Jonny Hayes every day is great for me. I learn every day.

“I know I’m fitter now as I can last a game a bit better now! I used to get to 60 or 70 minutes in and feel cramp. That’s expected as a young boy coming through. But you get fitter in training and in the gym and it all pieces together for you.

“European games are a good test as everyone is well organised and quick on the counter. So you have to be aware of that. I could be up attacking and then back defending a moment later. It’s demanding but that’s what you want as a player. That makes you better.”