It remains Paul Lambert's biggest footballing regret to this day.
The former Celtic midfielder would love to be the proud owner of a pair of European winners medals.
He has a Champions League gong as part of his collection after lifting the trophy with Borussia Dortmund in 1997 but the UEFA Cup is the one that got away.
It is now two decades on from the anguish that Lambert and his team-mates experienced in Seville as Martin O'Neill's men lost 3-2 to Porto after extra-time and to this day he doesn't speak about it all that much.
He said: "It's frightening that Seville was 20 years ago. Getting to a European final with Celtic was great but you have to win.
"It is one of the highest accolades you can get playing in a European final, especially with a club like Celtic.
"You can win the league anytime with Celtic. The Champions League trophy is the best and then you have the UEFA Cup which is now the Europa League trophy.
"It is a tough one to win.
"It is still my biggest regret in my career that I could have been the proud owner of two winners medals from the flagship European competitions and I am sad that didn't happen.
"It still lingers with me. You can never change history and Celtic gave it a go but it was not to be.
"To have a Champions League winners medal and a UEFA Cup winners medal would have been special."
"What else could I have done? Win the World Cup? That was no chance that was ever going to happen!"
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Celtic had the misfortune of playing against a Porto side managed by Jose Mourinho, who were in the ascendency.
As to emphasise how good a team Porto were around that time, Mourinho's men went on to lift the Champions League trophy the following season after their victory in Seville.
Eight of the side that defeated AS Monaco in the Arena AufSchalke in Gelsenkirchen also started against O'Neill's team the year prior.
Lambert remembers vividly how the stadium and city were ill-prepared for the invasion of some 80,000 Celtic supporters and that the surface for a showpiece European final left a lot to be desired.
He said: "It was such a shame that Celtic lost that night against Porto but it just wasn't meant to be for us.
"Porto were a top, top team and they had a manager who was on an upward trajectory.
"They had Brazilians in the side like Derlei and it was full of Portuguese international players like Maniche and Deco.
"Porto had Portugal's number one goalkeeper Viktor Baia and class central defenders such as Jorge Costa and Ricardo Carvalho as well.
"They were a great side. Celtic fans talk about their time-wasting antics but if we were winning at any stage in that game we would have done the same. You do what's necessary to win.
"The pitch was terrible. I remember training on the surface the night before and thinking it was really poor.
"It was bone dry and it was newly laid pitch and it hadn't knitted well. It was really sticky.
"The stadium itself wasn't big enough either to hold or cater for the Celtic fans. UEFA totally underestimated the amount of Celtic supporters that would travel to this game.
"To take a crowd of 80,000 knowing that half of them will not even get into the stadium for the final was incredible"
Despite O'Neill's side entertaining football fans all along their journey to Seville, they fell just short at the final hurdle.
However, Celtic had reached their first major European final since losing the European Cup to Feyenoord in the San Siro in 1970.
But it was Henrik Larsson, who bagged two goals on the night, that Lambert felt the most sorry for.
"We just fell short and on the night, we never hit the heights that we could have," he continued.
"On those kinds of nights, you have to bring your best to the table and we were so close but so far.
"Henrik turned up and scored two wonderful headers and how he scored the first header, I still don't know.
"How can you score two goals in a European final and still not win it?
"I think all the players contributed in their own way on that run to Seville. We had big moments along the way, like in Vigo with John Hartson's goal, we were hanging on against Stuttgart, but going up against Blackburn and Liverpool and winning both of those matches was brilliant.
"The team on the night in the final just didn't click and that's why we finished runners-up.
"It would have been a fitting way for Martin O'Neill's team to be remembered.
"That team put Celtic firmly back on the European football map. It was loaded with top players all over the park.
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"These guys were proper players who could handle anything. That team could have held their own against anybody. It was a powerful Celtic side.
"The 2003 team had a bit extra and we took them all on and we competed against the best of the best.
"That dressing room was strong and there were no bad characters in it which is why we all got along so well.
"The spirit in the 2003 dressing room was magnificent and they don't come much better than that."
Lambert has never watched either of the European finals he has appeared in back in full. He never will. He knows what he achieved in his career and nobody needs to ever remind him of it.
Yes, he still has the medals but it's the memories that are burned deep inside him both good and bad.
The 53-year-old said: "People always ask me about the medals and stuff but the biggest medal you have is your brain.
"Nobody can take that away from you. That's your go-to for all of your career. I only talk about 1997 and 2003 if somebody asks me.
"I never go out of my way to bring it up. I don't need to promote it as I know exactly what I did.
"There is a moment when Henrik Larsson held his silver medal up to the TV camera and he stared directly down the camera and said something like: "I didn't come here for this."
"That totally encapsulates how every Celtic player felt about Seville."
There is one almighty crumb of comfort for Lambert that he still clings to 20 years after his greatest career disappointment.
"People always say to me, what was the difference between the 1997 Borussia Dortmund Champions League winning team and the Celtic UEFA Cup team of 2003?" he said.
"The greatest compliment I can give is that the Borussia Dortmund class of 1997 were a special team.
"The Celtic class of 2003 was a great team. That's the only difference. That's the highest accolade I can give the Celtic lads."
That is high praise indeed for O'Neill's class of 2003, who came so close to glory.
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