The exact details are sketchy in his mind, but Callum McGregor will never forget the electricity that Seville jolted through the very fabric of Celtic.

As a nine-year-old, his evenings were spent in the shadow of Celtic Park where, 20 years ago, the likes of Liverpool, Stuttgart, Blackburn Rovers and Boavista were all sent packing on that mythical run to the 2003 UEFA Cup final. As its 20th anniversary approaches this Sunday, it is McGregor now wearing the captain’s armband then held by Paul Lambert, his formative years at Barrowfield coinciding with a landmark event in the club’s history.

It is one he recalls leaving him in no doubt as to the ‘magnitude’ of what he was aspiring to; the excitement of Martin O’Neill’s now-iconic team competing in a major European final against Porto trickling all the way down to the kids who hoped to one day follow in their footsteps.

“I was obviously still pretty young at that point but there was a huge buzz about the place,” the 29-year-old remembers. “When you're right at the very start of your journey and you see the first team in a European final, that tells you the magnitude of the club and where it was at the time. Some big players, a big manager at the time as well, and just a real feel-good factor.

“That filtered through all the youth teams as well. When you see the first team at that level straight away your mindset is that you have to get to that level. If that's where the first team is playing you have to try to push and progress as much as you can so hopefully one day when you step through that door as a first-team player you can try to reach the same level as what these guys did.”

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Catching a glimpse of O’Neill, a Henrik Larsson or Chris Sutton was rare, but the arena looming large just around the corner was symbolic, a constant reminder of what was possible.

“We were based at Barrowfield at that time,” he explained. “I know the first-team were as well but there were different training regimes and they were full-time and we were coming in at night as kids. We never really crossed paths but the important thing was we could always see Celtic Park in the background and the coaches used to say to us that we had to aspire to get to that level and get on the big stage. The training group being so close to the stadium was a good thing for us as well.”

Seville was an adventure that has never been repeated at Celtic, a likely factor in the mythical status that has formed over two decades. Success on the continent has been the one thing to elude McGregor in an otherwise glittering career.

There have been moments, no doubt, but too many have been of the ‘nearly’ variety. Financially, the odds are stacked against Scottish clubs in the European arena, but in reaching last season’s Europa League, Rangers showed that special things can happen.

It was, admittedly, a demonstration which cut bit too close to the bone for Celtic fans given it transpired in the very same city, but one that showed a Seville for the new generation need not be a pipe dream. McGregor admits he hopes to be the captain who can one day take them there.

“Every season you see European football is so highly contested,” he said. “There are so many big clubs spending a lot of money to try and win these tournaments. For Celtic, it's certainly in their history that they can compete at this level and I think that's the level for us to try and get to, and when we're in there, compete, and try and go as far as we can in these competitions.

“It's always a goal when you look at the start of the season to get out of the group stage, try and go on a run and see what happens from there. I think every summer we always have that ambition and that's the ambition of the club as well.”

Domestic dominance over their city rivals has been made to look remarkably straightforward by Postecoglou, but could he be the man to re-establish Celtic as a European force? The manager has made no secret of the fact it is a key aim in his long-term vision for the future.

“I think we all hope so,” McGregor continued. “We see how everybody in the building works and how he works. He's very on the ball in terms of recruitment and things like that. He's always trying to push the club forward and he's a real strong figurehead for the club which is exactly what this club needs.

“We just try to get better every time that we're together. Every game we play and every training session. He never puts any limits on what we can achieve so the more he pushes us then hopefully we can try and get to that level. I know he's an ambitious guy as well so hopefully with all that ambition we've got in the building, we can try and do it.”

Celtic’s return to the Champions League this season was, on paper, a chastening one. There were some harsh lessons learned, of course, but also hope to be found. Postecoglou was steadfast in his refusal to adopt a more pragmatic approach when faced with the might of Real Madrid, believing it to be the only way Celtic can learn to thrive on the big stage, as opposed to operating in permanent survival mode. It has left McGregor with a clear idea of what can be different next time around.

“Just experience from the group to be honest,” he said. “The only way you gain experience as a player is going through it and learning from the experiences live as they happen. That was the first time we did it as a group, hopefully there's been learning.

“I think some of our football was outstanding at times and we created a lot of chances so I think it's maybe just a case of being one year on, one year more mature as a group and hopefully we can find that finishing touch to the football that we played this season. As always we come back with a fresh mindset and hungry to do well and that's the same in that competition as well.”

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McGregor watched on this week as Manchester City set the standard for the entire continent in a brutal dismantling of Real, their ranks including his former loan team-mate Jack Grealish. The pair played together in a memorable spell at Notts County in 2013/14. They could yet be reunited in next season’s competition, and McGregor insists it was thrilling to see Grealish operating at the very highest level.

“It was brilliant to see him do so well,” he said. “The City football was outstanding. On a different level. A really high level performance and great to see Jack as a part of that as well. He was outstanding. I don't speak to him as much anymore. He's probably forgotten about me right enough now he's a superstar!

“We always look out for results, I'm sure if you asked him the same he'd always keep an eye out as well. We had a really good time at Notts County together so we're always really fond of each other and hope that we do well. I'm pretty sure if you asked him the same question he would be similar.”