The galling thing for Rangers is that a Celtic performance no better than moderate in level was sufficient to beat them. With Ange Postecoglou’s team only three points from retaining the league title, second-tier Inverness will sit between Celtic and a fifth domestic treble in seven seasons. This is an era of Celtic dominance; success in that Scottish Cup final early next month will take the club’s recent trophy count to 17 from a possible 21. Rangers, whose season is now over in all but name, remain a distant second best to their city rivals. In an Old Firm clash noticeably free from controversy, those in green and white celebrated once again. Rangers have tasted victory only once in the past nine stagings of this derby. Michael Beale has used a softly, softly public approach towards the players he inherited when appointed as manager in late November. Until now. He used his post-match media duties to talk of “the biggest rebuild this club has seen in a number of years” in the next transfer window. Beale insisted he needs “renewed energy and renewed ideas”. The sentiment was perfectly appropriate. Since winning the Scottish Premiership in 2021, Rangers have regressed. “This has been a disappointing season,” Beale said. “It has been a season that promised a lot more than it has given.” This is something of a theme. Despite having the second biggest budget in the country – and by a significant margin – Rangers have won fewer domestic honours than St Johnstone in the past decade. Beale’s acceptance of a need for seismic change looks like a positive step. Celtic’s trajectory has been completely in the opposite direction to their demoralised old foes. “This group of players have an unbelievable work ethic,” Postecoglou said. “They found a way to overcome the challenge again. They can be resilient as well as playing football.” The defining goal summed up Rangers’ problems. Inexplicably, a batch of their players stopped as the Celtic midfielder Matt O’Riley appealed in vain for a free-kick just outside the penalty area. Daizen Maeda stole in to snatch possession before crossing for Jota to head home. The Rangers backline appeared blissfully unaware of Jota’s position. “You can talk about mistakes but we instigate mistakes because the boys never switch off,” Postecoglou said. “It isn’t coincidence. We are always alert.” Three minutes before the break, Celtic had earned a crucial advantage. Beale’s exasperation was perfectly plain. “Fine margins will decide big games,” he said. “We made an error, again, in a moment and conceded. “It has happened in a lot of big games. Two or three players switched off. They are in the dressing room kicking themselves. Nobody means to switch off. We shot ourselves in the foot again.” Ryan Kent and Alfredo Morelos, who are both running out of contract, will lead the summer exodus from Ibrox. Kent lasted 45 ineffectual minutes here. After Morelos was substituted in the closing stages, Rangers played without an orthodox centre‑forward. This was a baffling situation for a club of such size. Nonetheless Rangers were not entirely without attacking threat. Within 30 seconds of kick-off, Nicolas Raskin saw a shot deflected narrowly wide of Joe Hart’s goal. James Tavernier curled against a post in the second period, with Fashion Sakala horribly wasteful from the rebound. Celtic never really promised to add to their lead – an Allan McGregor low save from Kyogo Furuhashi and a shot from the Japanese forward that flashed over aside – but a defence brilliantly marshalled by Cameron Carter-Vickers also looked perfectly capable of holding firm. Postecoglou confirmed Carter-Vickers will not play again until the next campaign as a long-standing knee injury will receive proper attention. “We have given ourselves a chance to have a special season,” Postecoglou said. “But we haven’t done it yet.” This is surely only a matter of time.