At full time a deathly hush seemed to descend over Ibrox: the realisation that a season’s efforts had come to nothing, that the title they spent a decade craving and coveting and finally claiming last year has now all but slipped from their grasp. For, after a performance of extraordinary maturity and resilience in the most hostile of settings, Celtic are six points clear in the Scottish Premiership. Their 700 fans, whooping and celebrating in their cramped little corner of Ibrox, knew as well as anyone that the game is up. Ange Postecoglou was asked afterwards where this left the title race. “We’re three points closer, mate,” was all he would say, but on this evidence Celtic look like worthy champions in waiting. Tom Rogic and Cameron Carter‑Vickers got the goals but it was at the other end of the pitch that they really distinguished themselves: endless blocks, endless clearing headers, discipline and cohesion and naturally a little gamesmanship when it was required. Their midfield, written off before this game as too slight and technical for a game such as this, was a superb second line of defence, never allowing Rangers to take control of the game despite Aaron Ramsey’s third-minute goal. For the blue half of Glasgow it was an afternoon of regrets and frustrations. Rangers were poor: lacking in finesse and movement, reduced for large periods of the game to a fusillade of abysmal crosses. The seething and screeching of the crowd hardly helped, paralysing every player with the sort of extreme stress that inhibits rather than inspires. There will probably be a lively debate over whether the absent Alfredo Morelos would have made a difference to a toothless attack. Equally the 11 on the pitch could have done so much more. This, ultimately, is the sort of game upon which this group of players will be judged. John Lundstram, otherwise excellent, also gave away the free-kick from which Celtic scored their winning goal and thus will his derby be remembered. Such is the brutal starkness of the Old Firm. Glasgow on derby day was its usual crock pot of malice and menace, nerves and nonsense. Late on Saturday night three Celtic fans were arrested at Ibrox for attempting to seal shut the turnstiles with expanding foam. Meanwhile the second half was delayed while stewards picked shards of glass off the pitch from a broken bottle thrown at Joe Hart. “It’s disappointing,” Postecoglou said. “I thought the atmosphere was unbelievable. This is a fixture that gets beamed around the world. You don’t need a couple of idiots.” But for all the shenanigans off the pitch, the songs one can print and the songs one can’t, it was actually a fairly regular sort of game, with very little of the cartoon physicality often seen in these fixtures. Perhaps that suited Celtic, whose brief would have been to neutralise the Ibrox crowd as quickly as possible and let Rangers stew in their own anxiety. In this respect perhaps the turning point of the game came as early as the seventh minute, when Rogic’s equaliser dramatically spiked a Rangers surge that was already threatening to set the terms of the game. Rangers were rampant in those opening minutes under the midday sun, full of energy and promise, scoring early through Ramsey, who for all his early struggles at Ibrox was in the right place at the right time in the right game. It was a lovely flowing move, started by Calvin Bassey with the cross coming from Ryan Kent, who was Rangers’ best player in the first half before fading in the second. Briefly Rangers threatened to kill off the game there and then, just as Celtic had done in their last meeting in February. Instead, from Celtic’s first attack Rogic bundled the ball in, reducing Ibrox to stunned silence. Slowly and by degrees Celtic got themselves into the game. Three minutes before half-time Rangers failed to clear a free-kick and Lundstram’s hashed clearance was swept in by Carter-Vickers, the American centre‑half on loan from Tottenham. The second half began with another Rangers flurry but, despite a good save by Hart from the substitute Fashion Sakala, it was Celtic who had the better of the chances. The disappointment for Rangers will be that they offered so little in a game that mattered so much. “It’s not over yet,” the Rangers manager, Giovanni van Bronckhorst, insisted. “But we have to keep going, because there is still a lot to play for.” Van Bronckhorst was right, of course. There is a Europa League quarter-final against Braga on Thursday, points and pride to be salvaged, perhaps even the chance for a little revenge on Celtic in the Scottish Cup semi-final in a fortnight. But for now, and probably for this season, Glasgow is green.