Rangers’ Kemar Roofe leads the way in spanking of 10-man Celtic

There is a perfectly plausible scenario whereby Celtic, armed with new manager and a vastly superior squad of players to the one which capitulated at Ibrox, reclaim Scotland’s top flight title in front of giddy supporters in little over a year’s time. Even if that transpires, though, the ease with which this club conceded such a dominant domestic position must not be glossed over. Someone, somewhere – or perhaps umpteen people in umpteen places – fell asleep at the wheel.

It should not take embarrassing Old Firm defeat to emphasise this fall from grace. However, there is little doubt performances like this sharpen focus. Rebooting is easier in Scotland because of the general paucity of opposition but Celtic’s dishevelled status is shocking given the leeway – financial and otherwise – they enjoyed for so long. By full time, they had slumped to their heaviest Old Firm defeat since 2007. Twelve months ago, Celtic were revelling in a ninth championship in a row.

In the midst of a 4-1 tanking, two Celtic players typified the wider picture. Scott Brown, the captain, was playing in his 44th and final Old Firm game before he swaps hoops for Aberdeen red this summer. Brown’s only real ‘crime’ is susceptibility to Father Time – he turns 36 in June – but the club’s reliance on such a diminished midfield presence has been curious for a while. Brown lasted just 60 minutes here, by which time his key moment involved being bamboozled by Alfredo Morelos before a Rangers goal. There would not have been much broader sympathy for the Celtic captain as he trotted towards the bench, given his propensity to lord it over opposition players when times were somewhat easier.

Related: Rangers 4-1 Celtic: Scottish Premiership – live!

Kristoffer Ajer doesn’t have Brown’s age-related excuse. The Norwegian centre-back was linked with Norwich and Newcastle – not Premier League titans but Premier League clubs all the same - in the lead-up to this fixture, logical given his physicality, youthfulness and international experience. After Morelos took care of Brown, he watched Ajer duck under a shot which duly flew into the roof of Scott Bain’s net. With men like Ajer in the trenches, it is no wonder Celtic have lurched into crisis. As the half-time whistle blew and Ajer headed straight towards Nick Walsh, the referee, it was easy to infer self-awareness may not be the 23-year-old’s strong suit. Fine defenders carry out basic defending before daring to accost anybody else.

Celtic’s mitigation arrived from the red card issued to Callum McGregor seconds after Kemar Roofe opened the scoring for Rangers. McGregor, already on a booking after a foul on Ryan Kent, needlessly went to ground and upended Glen Kamara. Walsh played advantage, Roofe subsequently turning a Kent cross home with his chest. “Rangers were more clinical once again but the sending off is the big point in the game,” said John Kennedy, Celtic’s interim manager. Kennedy disputed the first booking, which he claimed Walsh told him was issued for a “reckless” challenge. “I don’t see any recklessness,” Kennedy added. This, of course, doesn’t explain McGregor’s later rush of blood. The truth is Old Firm matches generally involve a more lenient refereeing tone than applies elsewhere; Walsh bucked the trend.

Kennedy initially watched Celtic respond positively as Odsonne Édouard bundled home a close-range equaliser. Yet Rangers’ advantage at the break was merited, Morelos delivering the left-foot finish after Brown’s confusion and Ajer’s lack of fortitude.

David Turnbull’s wide diving header from a James Forrest cross, proved Celtic’s key moment of wastefulness. In Rangers’ next attack, Roofe deceived the visiting defence with a late run before meeting Borna Barisic’s cross. Rangers’ superiority was pressed home in stoppage time. Jermain Defoe, in what may be one of his final acts in light blue, was the beneficiary after Ismaila Soro conceded possession when under no pressure at all. Having shrugged off Stephen Welsh, Defoe slotted home with time-honoured calmness.

“It was a really strong performance,” said Steven Gerrard. “It doesn’t matter what’s at stake. We ran away with it in the end.” The ex-Liverpool captain has now guided Rangers to their first unbeaten season against Celtic since 1999-2000. Rangers have just two more Premiership games to negotiate as they look to keep their ‘loss’ column empty. Not so long ago, this kind of thing was Celtic’s domain; how swiftly the tide has turned.