Old Firm derbies are never decided by those on the periphery of the action. It is why Rangers find themselves in the tantalising - and, given the circumstances of their season, remarkable - position of engineering a two-point advantage with three games remaining.

In the immediate aftermath of a colossal 1-0 win at Ibrox, it was not the failings of those who made up the opposition but the absences that dominated the defending champions' post-mortem. The suspension of Scott Brown may not have had a destructive effect on last season's decisive derby matches but only the foolish would claim the ineligibility of the PFA Scotland player of the year did not contribute to Celtic's flimsiness.

Stephen McManus' most fervent critics could not put up a case for a defence weakened by the absence of their captain.

Then there was the unexpected return of Shaun Maloney for his first start in six months or, more accurately, the manager's decision to sacrifice Aiden McGeady to accommodate him. It was a decision that backfired on Gordon Strachan and the recriminations will linger on regardless of the destiny of the Clydesdale Bank Premier League championship.

For Walter Smith, there was only enthralment at his players' courage on Rangers' day of reckoning. Steven Davis scored the goal that fundamentally changed the dynamic of the title race. He had only two meaningful interventions: scoring the winning goal and denying Jan Vennegoor of Hesselink an equaliser by sweeping off his own goal-line minutes later.

There were other, less vaunted acts of heroism.

No-one afield was as swashbucklingly brilliant as Maurice Edu. Since his $5m transfer from Toronto FC, where he had earned the distinction of MLS Rookie of the Year, Edu has often appeared out of sync with the unreconstructed madness of Scottish football. The midfielder recommended to Rangers by Maurice Johnston found his own mojo at the Ibrox coalface. Edu started strongly, with an innocent abandon and fearlessness, and closed out the game with the assuredness and intelligence of a veteran.

He withstood a nasty foul from an unconvincing Glenn Loovens in the first half and blossomed into a pillar of reliability. An early booking for Paul Hartley neutered the midfielder's natural abrasiveness, but even so there were times when the 32-year-old was simply outmanoeuvred and overpowered by his strapping young adversary.

Marc Crosas was neat and tidy but because of Edu's forcefulness, did most of his good work in an area that caused Rangers no harm.

Edu played the biggest role in stifling Celtic. Yet, a stellar collective display from the chorus line would have been as pleasing to Smith, an unashamed aficionado of the Catenaccio, as the sight of Davis sidefooting Kenny Miller's cross over the line after 38 minutes.

David Weir, on the weekend of his 39th birthday, had enough puff to wear down Vennegoor of Hesselink and still have enough in reserve to blow out the individual candles on his cake. Madjid Bougherra simply reiterated why he is this year's Carlos Cuellar, if not more domineering and mobile than the Spaniard.

Steven Whittaker provided the most diligent performance of his Rangers career, stalking Shunsuke Nakamura into submission and popping up with a trademark run and shot that pinged off Artur Boruc's post.

Christian Dailly deserves special acclaim. The 36-year-old is the latest to endure the curse of the Rangers right-back. He was barracked for a shambolic performance against Hearts last weekend but drew on his experience to overcome a nervy start and an awkward opponent in Maloney. None the less, Strachan did Dailly a massive favour by omitting McGeady.

Smith's decision to drop Andrius Velicka, who has scored in each of his last four appearances, barely rated a mention in the media room as the Monday morning quarterbacks expressed their dismay at the disappearance of McGeady from the team sheet. It was not a printing error but it was an error none the less. Celtic enjoyed handsome possession.

In games of such magnitude, there is a world of difference between handsome possession and tangible dominance. Crosas stroked the ball around confidently but not threateningly. Hartley was unable to impose or express himself after receiving a caution inside two minutes.

In contrast, Edu was content to throw his weight around, invariably joined by Davis and Steven Smith, the full-back whose continued presence in midfield did not hit the headlines but successfully disrupted the interaction between Andreas Hinkel and Nakamura.

Towards the end, the Japanese was in danger of submerging into a soggy Ibrox pitch. There was a disjointed flow to Celtic's play and after two penalty claims involving Scott McDonald fell on deaf ears - the Australian grappled inside the box by Whittaker and then, more vigorously, by Dailly - Rangers' luck appeared to be in.

So it proved in the fateful seven-minute spell before the interval. Miller, vindicating his inclusion with an industrious shift alongside a workmanlike Kris Boyd, collected the ball on the left and his inviting cross was slid home by Davis who began his celebrations inside Boruc's net. The Northern Irishman was in the right place moments later, this time sweeping Vennegoor of Hesselink's header off the line.

The Dutchman was denied again by Neil Alexander. In the continued absence of Allan McGregor, he is proving increasingly dependable.

Boyd was presented with a glorious opportunity to put the game beyond Celtic, and end the lingering blemish on his goalscoring record, but after bustling clear of Gary Caldwell, a moment's hesitation allowed Boruc to smother his left-foot shot.

As Celtic's gameplan fizzled out against an obdurate Rangers defence, McGeady replaced a tiring Maloney but he had insufficient time or ingredients to cast any spells. Lee Naylor's subsequent introduction for Darren O'Dea only added another bizarre twist to Strachan's strategy, as Barry Robson and Willo Flood were instantly rendered unusable on the bench.

Rangers survived a desperate siege near the end, which eventually involved Boruc playing centre-forward, and the celebrations from the stands at full-time encapsulated the gravity of the victory. Rangers are now in prime position to atone for last season's collapse and deliver the first championship of Smith's second term of office. The Rangers manager is well aware there are roadblocks on the horizon.