Scottish Premier League/Rangers 0 Celtic 1: Roy Keane strode victorious from the frenzy, departing with a punch of the air in the direction of the swaths of Tricolours as the Celtic contingent briefly broke from bellowed chants of "champions". Last April similarly raucous celebrations in this arena proved horribly misplaced, though there is little chance of a sting in this season's tail.

So shambolic are Alex McLeish's side these days that Keane and Wayne Rooney, a guest of the former Manchester United captain, may even have found their first taste of Glasgow's bitter divide tinged with anti-climax. This game lacked the usual furious spite, though an utterly professional victory has hoisted Celtic 13 points clear of Hearts and a staggering 21 ahead for the dishevelled home side with 12 games to go.

"There was a big swing for us this weekend," admitted Neil Lennon. "It's up to us to shore up that advantage now."

With Keane snarling in their ranks, there should be no repeat of last year's capitulation. The Irishman was booked for a trip on Dado Prso after the hour mark as the Croatian threatened to break unchecked into Celtic territory, though the cuteness of the foul rather summed up the 34-year-old's selfless display. This was an unflustered performance, altogether devoid of the emotion that might have been expected on his first appearance in the fixture.

The cold glint was back in his eye, his partnership with Lennon in the centre - 68 years between them - suffocating Rangers and driving their supporters to distraction. Doubts must remain as to how the pairing will cope with raw pace but the home side's tempo was sluggish at best until the final frantic few minutes.

"Roy's given us presence and know-how," said manager Gordon Strachan. "As I left the training ground on Friday Dion Dublin and Roy Keane were sitting there speaking to a couple of the youth team lads and they were hanging on Roy's every word. It's that knowledge that's invaluable."

Keane was just as quick to impart advice to his colleagues on the pitch, with snapped rebukes for the slightest error or dawdle in possession. Paul Telfer was castigated early on, with Keane lambasting Lennon when Celtic began to drop dangerously deep after the interval, putting their first clean sheet since mid-November under threat.

"You wouldn't want to change the way he is," said Lennon. "His shouting gets a reaction. It's up to you whether it's positive or not. The boys respect him for what he's done and what he is. He's a great player. If he wants to give you a rollicking, you respect that."

The home fans were as eager to tear into their players, though the disgust which welled on three sides of the ground was understandable. This was McLeish's last Old Firm spat at Ibrox, his departure confirmed for the end of the season. Defeat was also Rangers' third in succession, without a goal en route, the sloppiness down the spine of the side inexcusable. Marvin Andrews and Sotirios Kyrgiakos wheezed their way through the contest, the Greek departing early - appropriately enough with "respiratory problems", according to the manager - and with Barry Ferguson and Bob Malcolm incapable of wresting control.

Celtic's goal was suitably comic, Malcolm blocking Stilian Petrov's shot with Andrews and Kyrgiakos disoriented, allowing Maciej Zurawski time to slide in his 11th of the season. The hosts only sporadically suggested they might equalise. Thomas Buffel's run and flick across goal might have yielded reward but Nacho Novo was too far behind play to capitalise.

In the final minute Chris Burke chipped into the six-yard box and a trio of Rangers players might have converted, only for the blue muddle to confuse themselves. Prso's shot duly dribbled behind.

RANGERS: Waterreus, Hutton, Andrews, Kyrgiakos (Rodriguez 66), Smith, Burke, Malcolm, Ferguson, Buffel (Kris Boyd 72), Novo (Lovenkrands 61), Prso. Subs not used: Klos, Hemdani, Murray, Namouchi. Booked: Prso, Kyrgiakos, Kris Boyd.

CELTIC: Boruc, Telfer, Balde, McManus, Wilson, Petrov, Keane, Lennon, Maloney (Pearson 89), Zurawski, Hartson (Dublin 74). Subs not used: Marshall, Thompson, Nakamura, Wallace, McGlinchey. Booked: Keane. Goal: Zurawski 12.

Referee: M McCurry (Scotland).