IT was September 18, 2011. Rangers had been crowned Scottish champions for a third successive season a few months previously and made Ally McCoist their new manager. Europe had been a wash-out but in the league they had followed an opening-day draw with Hearts with five successive victories, all achieved without the loss of a goal. When Celtic then came to Ibrox for the first Old Firm derby of the season and were beaten 4-2, optimism soared even higher. But it would prove misplaced. That derby, almost exactly five years ago, would be the last time the two teams – the two clubs – would meet as equals. Rangers would never again hold the upper hand.

If the battle for Glasgow supremacy can be compared to an arms race, then in speculating to accumulate the team from Ibrox had overstretched themselves. The financial strain on the club was already evident early in the 2011/12 season, the possible seismic repercussions of the Big Tax Case hanging over them as Craig Whyte took his first faltering, unsteady steps as chairman. On the field, though, Rangers seemed initially unfazed by the ongoing background commotion, and by early November they had racked up a 15-point advantage over Celtic.

Soon, however, the first cracks started to appear in the McCoist tenure. A Celtic team aggrieved to have lost the title by a single point the previous season were not slow to take advantage. When the sides met again at Celtic Park just after Christmas, a Joe Ledley goal was enough to send Celtic to the top of the league. They would remain there for the rest of the season. Any prospect of a Rangers’ fightback was ended by a 10-point reduction for going into administration, and by the start of the following season their financial mismanagement had resulted in them being made to serve their penance in the lower leagues.

Now back in the top division, Rangers will travel to Celtic Park on Saturday for the first league derby between the sides in almost four-and-a-half years. The competitive nature of the contest will mean they will have a chance of winning but, in terms of both financial clout and playing resources, Rangers now find themselves undoubtedly in Celtic’s shadow.

“It’s probably a fair assessment to say the start of the 2011 season was the last time the two clubs were on a level footing,” said Mark Wilson, the former Celtic defender who played in that 4-2 Ibrox defeat but who by the end of the season would be picking up his fourth league winner’s medal. “The teams were pretty evenly matched and I don’t think there was a clear favourite at the start of that campaign. Rangers had a decent squad and I remember by October or November time they already had quite a big lead over us.

“But the boys were able to claw it back and when Joe scored the winner in the next derby just after Christmas we were back on track. From that point on, Celtic have gone one way and Rangers have gone the other. The chasm became huge over the years that Rangers spent down the divisions. It’s grown a bit closer now as Rangers are in the same league but there is still undeniably a gap in Celtic’s favour.”

Contrary to what was said publicly at that time, the ongoing financial unrest unfolding at Ibrox throughout the 2011/12 season did not go unnoticed within the Celtic dressing room.

“Loads of players will say they didn’t take any notice of these things but it was impossible to ignore,” said Wilson, now a radio and TV pundit with the BBC and Radio Clyde. “It was our main rivals who had pipped us at the post the last time and we were desperate to make amends. You couldn’t help but follow this dramatic story as it unfolded. It was a catastrophe for them.

“But if Rangers hadn’t had those problems and not been docked the points, we felt that we would have gone on to win it anyway. Maybe Rangers got distracted but Celtic were relentless. We didn’t take our foot off the pedal or give them any encouragement at all.”

While Rangers were plotting their way through the lower leagues, Celtic were amassing fortunes through regular European football and sizeable transfer fees. There is an argument that, given that financial advantage, the gap between the sides should be even wider as they prepare to recommence hostilities but Wilson felt his old club have taken the correct, prudent approach.

“I don’t think there was any need for Celtic to go out and spend millions and millions when they didn’t need to,” he added. “I think that would have been bad management. If they had gone down the road of blowing more money quite possibly they could have ended up in the same place as Rangers further down the line. So it was wise for Celtic to achieve success without breaking the bank.

“I still feel the gap between the clubs is pretty big. Rangers might be able to win a one-off game as we saw in last year’s Scottish Cup semi but over the course of a season Celtic have got the strength in depth in their squad, and the finance to come out on top.”