It was one of those days when Arsenal might have played for another 90 minutes and failed to score. It was all so deeply frustrating for Mikel Arteta and the home support. The sting in the tail, however, would devastate them, sparking boos at full-time and the feeling that the club have stumbled into a mini-crisis. Liverpool’s joy knew no bounds. There had been the impression that this FA Cup tie was more important for Arsenal, given the form that they had taken into it – three Premier League defeats in five. The need for them to recover momentum was greater. Liverpool, sitting pretty at the top of the table, also had the security of their shot at Carabao Cup glory; they face Fulham in the first leg of their semi-final at Anfield on Wednesday. It was Liverpool who rode out the Arsenal storm or, to put it another way, watched them repeatedly lack the needed ruthlessness in front of goal; for Arteta, it is an increasingly worrying trend. And then Jürgen Klopp’s team hit them hard. The opening goal on 80 minutes was a body blow for Arsenal, the excellent Trent Alexander-Arnold whipping in a free-kick from the left and Jakub Kiwior, under no huge pressure, directing an attempted clearing header into his own net. The die was cast. Top of the league at Christmas but now down to fourth, Arsenal have had a sinking feeling. Luis Díaz would add further insult at the bitter end, lashing into the near top corner after a break involving Darwin Núñez and the substitute Diogo Jota. In a sense this was the hors d’oeuvre before the main course of the league meeting between the clubs here on 4 February. But if it was Liverpool laying down a marker – and doing so without Virgil van Dijk, who was ill, Mohamed Salah, who is on Africa Cup of Nations duty, and a host of others – it has to be said that the FA Cup still matters. Arteta had described last Sunday’s league defeat at Fulham as the low point of the season, a “painful and sad day”, and he got a reaction from his players, Arsenal storming out of the blocks, the flashing lights on the underside of Bukayo Saka’s boots not the only eye-catching detail. The winger would change into a more conventional pair later in the first-half. Yet it was possible to wonder at an early juncture whether they would live to regret their profligacy. Martin Ødegaard should have scored on 11 minutes, thumping onto the crossbar when well placed, and it was not the only good chance that Arsenal created in the early running. Reiss Nelson, starting ahead of Gabriel Martinelli on the left, almost rounded Alisson at the very start, following a long ball by his club’s domestic cup goalkeeper, Aaron Ramsdale, while he would see another effort deflect wide. Kai Havertz also worked Alisson with a curler. The major team news item had been Liverpool’s loss of Van Dijk. “It’s difficult for Virg to look shit but he did,” Klopp said. The Liverpool manager would reel off a long list of other absentees and he loaded his substitutes’ bench with youngsters. Conor Bradley and Bobby Clark would get on in the 75th minute. Jarell Quansah emerged with honours as Van Dijk’s deputy in central defence. Arteta used Havertz up top in the absence of the injured Gabriel Jesus and he had decent chances to score before the interval. Twice Havertz dallied before shooting without much conviction and there was the moment when he headed wide on a corner after levering Quansah out of the way. Ben White had won it when he forced Alisson to tip over a rising drive. Klopp lamented Liverpool’s inability to get their press right in the first half, beginning with the front players, and it was practically all Arsenal before the interval. Yet Liverpool, for whom Núñez had glanced wide on a 22nd minute corner, almost stole the lead at the end of the half. Alexander-Arnold ran on to an inviting ball up the inside right and unfurled a venomous shot that made a serious mark on the crossbar. Alexander-Arnold had done something similar in the 1-1 league draw between the teams at Anfield before Christmas. Arsenal, wearing an all-white kit as part of their No More Red anti-knife crime initiative, continued to push at the start of the second half. It turned into a psychological test, as much as anything else, and it was draining to watch Arteta on the touchline. Twice Saka blew opportunities after crosses to the far post. Klopp reshuffled. On came Jota in the No 9 role, Núñez moving to the left. On came Ryan Gravenberch as the left-sided No 8, Curtis Jones moving to No 6. Slowly but surely Liverpool grew in confidence, from back to front, and they began to advertise the breakthrough. Núñez missed a pass to Díaz on the break. Jota sliced from left to right and fed Díaz, whose low shot was brilliantly saved by Ramsdale. From the ensuing corner, Jota rose to head against the crossbar. Arsenal were gripped by angst. They would eventually be overwhelmed.