It's been a long, long week in Glasgow, an Old Firm double headache of a week. This has meant that the usual thirsty anticipation for the weekend, difficult enough to suppress, has been laced with some spiky midweek action. What a cocktail.

On Wednesday night the pouring began in earnest at Hampden Park. A semi-final of a competition that does not even offer entry to the UEFA Cup as its ultimate prize - a competition worth "a bottle of whisky" to Rangers' manager Dick Advocaat beforehand - contrived to be important enough for three players to be sent off and for 41 fans to be arrested. Thursday morning was a collective plea for calm.

Understandably so, because if Wednesday's fixture managed to make itself significant, then what tomorrow's potential title-decider will do to folk is not worth contemplating. That, as they say, is a police matter.

By deliberate contrast, the players, the clubs and many supporters did their best to keep themselves focused on football matters. Only tomorrow itself will reveal how much it has been informed by Wednesday, on and off the pitch.

What is certain is that a title-decider in early February is normally a concept to keep at bay. But Celtic's nine-point advantage lends this fixture that status. If Celtic win. The objective supposition is that that will happen and, if so, it will send Martin O'Neill through another hoop on his way to being lauded as Jock Stein's true successor: A premature canonisation, of course.

But the remarkable turnaround in Celtic since O'Neill picked up the baton dropped by John Barnes and Kenny Dalglish is there for all to see. However, in a large week for the Old Firm this is best done not by looking at events on Wednesday, or whatever tomorrow brings, but rather by looking at Thursday.

The day itself, featuring confirmation of the suspension of Michael Mols, Claudio Reyna and Lubo Moravcik, contained enough on its own to be relevant to tomorrow. But lost amongst the red cards and disciplinary points was the fact that Thursday was a special date for the 2001 version of the Old Firm. Thursday was the anniversary of the scoreline: Celtic 1, Inverness Caledonian Thistle 3.

That such recent Celtic trauma merited not a mention in the multitude of publications dedicated to it and Rangers in itself is a reliable barometer of the green transformation under O'Neill. Not one of the Celtic 11 - or the 12 if you include Ian Wright, who came on for the disaffected Mark Viduka - who played in that game will feature tomorrow.

Perhaps an argument could be made for Tom Boyd, though he will only appear tomorrow if Joos Valgaeren has not recovered. Similarly, Moravcik, had he not been suspended, would have been on the bench. But that Celtic side - Gould; Boyd, Riseth, Tebily, Mahe; Blinker, Healy, Berkovic, Moravcik; Viduka, Burchill - is unrecognisable from the one that O'Neill will field 12 months on.

A year ago O'Neill was preparing Leicester City for a victorious League Cup final against Tranmere Rovers. The qualities he bred in that Leicester side - commitment, defiance, energy and some skill - are those which he has transfused into Celtic Park. They had been conspicuous by their absence under Barnes.

Yet, for a man who is a brilliant talker, O'Neill has been remarkably restrained in his comments about the reconstitution he has overseen in the past seven months. He has yet to give a solo newspaper interview and his press conferences have usually been a reiteration of his initial audit on just how far Celtic have to travel before they can be considered Rangers' equals. "As I've said ad nauseum," is a frequent O'Neill prefix.

But a fortnight ago, after Celtic's Scottish Cup tie at Stranraer - won efficiently 4-1 - O'Neill said the following: "You're always apprehensive about these kind of matches, particularly after Inverness Caley. But it would have taken people four or five minutes to see the same scenario wasn't going to present itself again." O'Neill's quality is that he made sure it did not happen again.

The blue half of Glasgow is impressed. Rangers' chairman David Murray yesterday went as far as to say that O'Neill's arrival at Parkhead has turned the Old Firm upside down. Celtic are in the ascendancy now, Murray argued, on the pitch and as a club.

Terry Butcher, the Rangers captain under Graeme Souness and still domiciled in Scotland, spoke of the virtual revolution O'Neill has instigated since joining.

"It's amazing when you think of that game," Butcher said to The Irish Times of the Inverness result, "Martin's changed Celtic around. Above all he's instilled steel. He's bought a spine - Douglas in goal, Valgaeren, Lennon and Sutton. He's also bought Thompson and Agathe. They're his players and it's his team.

"Martin has given them confidence and self-belief, and in a very subtle way he has altered things behind the scenes. He's very clever, he's been very level-headed, doesn't say much to the press and he doesn't make false statements. He saves a lot of his talking for the dressing-room. He's got his shape, 3-5-2, got his system that's worked very well. It's his blueprint."

That's quite a list of compliments.

O'Neill's green blueprint also features attitude. Yesterday at Parkhead as he did his utmost not to talk up tomorrow - "It's premature to talk about a championship decider"; "I hope it doesn't spill over"; "we're miles behind Rangers"; "we're not good enough to go on the field and play in second gear" - he acknowledged that when he watched videotapes of Celtic's performances last season he recognised an aggression deficiency.

"What I thought I saw in the videos were players who were very good when on the ball. But when they lost it nobody did very much about getting it back, for long periods. If you want to be a top-class side then one of the prerequisites is that you're able to play without the ball. It was a stronger mentality I wanted, more than actual physical strength."

Asked if he considered he had brought a big game mentality, O'Neill replied: "More a game mentality. Listen, Rangers didn't win the league by 21 points last year because they were a wee bit lucky. Celtic lost games at places other than Ibrox."

Yet there is no denying that O'Neill has also recruited physique. Against Hearts last Sunday it was notable how much bigger the Celtic players were physically. After Wednesday night's fractious encounter, the most common observation was that Celtic now appear to be physically tougher than Rangers.

Neil Lennon, O'Neill's will on the field, personifies this. As Charlie Nicholas said: "Lennon is sensational. He looks half a stone overweight and doesn't impress as a natural runner. Yet he covers every blade of grass. He reminds me of O'Neill's assistant at Parkhead, John Robertson. He didn't look like much of a player either, but he most certainly was."

If Lennon shows anything like the dominance he displayed at Tynecastle then Celtic should find themselves 12 points clear on Monday morning. Lennon got the better of Barry Ferguson on Wednesday evening and, as the story goes, justified his £5.5 million signing at a stroke.

O'Neill, apparently, went to see his board after Celtic's 5-1 hammering at Ibrox and said that if he had Lennon, then Ferguson would never be able to run an Old Firm game again. Lennon made his debut a fortnight later.

That is another indication of Celtic's culture change under O'Neill. The fact that they have spent heavily, look set to take control of the rivalry, and are leading by a snug margin are just some of the reasons why Glasgow's joke of the week has been that when Celtic stare into the mirror they see Rangers of a year ago staring back.

And vice versa.