As Celtic and Juventus left the field at the end of the first half of their frenetic and pulsating Champions League group game last Wednesday night, the singing and general tumult took a few minutes to subside. That euphoria, which had erupted after the home side had taken the lead just before the break, was then replaced by excited, half-believing chatter.

The moment, however, was swiftly destroyed and the spell broken by the half-time warm-up man who bounced up with information about the next home game. "Tickets," he said almost embarrassed, "are still available for next week's visit of Stirling Albion in the CIS League Cup." A collective groan could be heard rumbling around the crowd. Welcome back to reality.

The counter-point between one of the best teams Italy has to offer and Stirling was probably extreme, but substitute the names of the any of the sides Celtic have to face week in, week out in the Scottish Premier League and the reaction was unlikely to have been any more positive. Motherwell, Kilmarnock, Livingston, Dundee - the list goes on, and the harsh truth is that in Scottish terms it includes everyone else bar Rangers. And if Celtic fans had their way they would try to do that as well.

There is, of course, a fairly obvious contrary argument to this, along the broad lines that Celtic and Rangers want to sprint off into the distance having just about learned to stagger around on their own two feet, and that their new-found arrogance shows a lack of respect for their fellow Scottish clubs. Up until now this has probably been truer of Rangers than Celtic, as their superiority was grounded in a run of nine consecutive league titles in the 1990s. This ensured that they had a glimpse of how modern European football was and the direction in which it was going. They liked what they saw and made no attempt to disguise their desire to break free of their domestic shackles.

Celtic, though, were a lot more reticent and much less sure-footed. Years of disastrous under-achievement and a process of ignominious descent which showed no sign of being arrested had trampled the club's spirit.

Significantly fewer than the 60,000 who thronged Celtic Park last Wednesday were present at Barnes' final game in charge at the start of last year. Incredulous laughter and hoots of derision would have been the immediate response if you had told anyone who watched Celtic being frog-marched out of the Scottish Cup by Inverness Caledonian Thistle that they would be sitting in the same seat 20 months later facing Juventus. But so it has come to pass.

For decades Celtic have been like an ambitious but ultimately misguided boxer trying to go in above his true fighting weight. The fans have boomed and blustered about this player or that player being as good as any plying their trade in top-level English football, but with hindsight it can be seen to have been a mass act of self-delusion.

The other trump card perceived to be in the Celtic deck was the club's huge and loyal fan-base. But in the years after the double of league and championship in 1988, Celtic's centenary year, even that staple of the club's existence came into question. By Scottish standards crowds of 30-40,000 were still streets ahead of the rest, but for a club with European ambitions those were not gates capable of sustaining a credible operation.

Three things happened in parallel to stymie these worrying trends. The first was the emergence of Henrik Larsson. Signed in July 1997 for a paltry £600,000 sterling, he has since gone on to under-pin two championship winning sides and stake a claim as the best striker in Celtic's history. Certainly his goal-scoring record is more than a match than anything that has gone before, and the adverse circumstances in which those goals were scored has also to be factored into any judgment of his historical importance.

But his greatest contribution has been wholly intangible. His innate ability and the joyful way he goes about his work have made Celtic and its supporters feel good about themselves again because in Larsson they had a striker comfortable in the best European company. That he remained loyal to the club was a bonus, because it showed that Celtic had a future in its own right and not just as a feeder for the bigger European outfits.

The second development has been the re-emergence of Celtic's Irish dimension over the past decade or so. In relatively recent times that Irishness had come to be regarded as something of an irrelevance, but under former chairman Fergus McCann the club began to explore and redefine its Irish relationships. The fruits of that are now becoming apparent as Celtic attract increasing numbers of Irish supporters whose fortnightly journeys to Glasgow have had an important effect on attendances. A happy by-product of this new dispensation has been the gradual eradication of sectarianism among Celtic's Irish support. That has helped the club to modernise and reshape itself into a credible European force.

Not even Martin O'Neill, the third cog in the wheel, could have countenanced such rapid progress. Last season's treble exceeded expectations, as did the fact that Celtic came within touching distance of making the next phase of the Champions League. Wins over Porto, Rosenborg and of course Juventus suggested that the club is not out of place in elevated company, but the nature of the away defeats against the same opposition were vivid indications that O'Neill's Celtic are by no means the finished article.

The extent to which some of the patently obvious failings would been further highlighted by continued involvement in the Champions League will never be known, but perhaps in all the circumstances it's better that they didn't find out.

The UEFA Cup remains a worthwhile consolation target, but O'Neill's primary focus will surely now be on retaining last year's league title and ensuring another tilt at the Champions League next year. And while the supporters will face into that domestic slog with all the enthusiasm of a roomful of GAA delegates about to debate Rule 21, the Scottish Premier League has to remain Celtic's most important target. At least until something better comes along.