Arsenal being Arsenal, it was never going to be straightforward. For much of the evening Arsène Wenger’s players did their best to emulate Barcelona’s performance at Roma on Tuesday in a way that nobody at Arsenal would have wanted as CSKA Moscow threatened to overturn a three-goal deficit and inflict the sort of humiliation that the Frenchman would have struggled to survive.

Yet with CSKA two goals to the good, courtesy of close-range efforts from Fedor Chalov and Kirill Nababkin, and chasing the decisive third blow that would have seen Arsenal eliminated in the most remarkable fashion, the Premier League club found salvation in the shape of Danny Welbeck. Relief coursed through Wenger, his staff and the Arsenal players after the England forward scored 15 minutes from time to give them the breathing space that they so badly needed.

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By the time Aaron Ramsey sprinted clear of the CSKA defence to add a second, deep into injury time, Arsenal were no longer on the path to self-destruction and the 300 or so travelling supporters could celebrate the prospect of a first European semi-final in nine years. To say that Arsenal made hard work of things, however, barely does it justice.

This was a desperately poor performance from an Arsenal team who seemed to be sleepwalking their way through the game for long periods. There was so little conviction and intensity about their approach – they failed to register a shot on target in the opening 45 minutes – and a sense of panic set in from the moment CSKA took the lead.

Arsenal were toothless until Welbeck scored, overrun in midfield and an accident waiting to happen at the back, where Petr Cech also endured a difficult night. The Arsenal goalkeeper was far from alone in that respect, however, and it was alarming to see a limited CSKA Moscow side cause so many problems.

Yet all that matters for Wenger and his players now is that Arsenal’s hopes of winning the Europa League remain alive – leaving the door open to qualifying for the Champions League next season – and that next month’s final in Lyon is one step closer, with the draw for the semi-finals taking place in Switzerland on Friday and Atlético Madrid the team to avoid.

Whoever Arsenal face next, they will have to play far better than they did here. “I feel that maybe we were a bit surprised by the intensity and not at the races in the first half,” Wenger said. “They scored the second and even then they have another chance to make it three.

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“Then we were a bit on the ropes but we had a good response. If you look at the game we were in trouble but once we moved to a five [at the back] we looked much more stable and didn’t give so many chances away. We have players who can always score and once we scored the first it was a big blow for them and they didn’t recover from that.”

The onus had been on CSKA to take the game to Arsenal because of the 4-1 deficit from the first leg, yet that rarely looked like happening in a drab opening half hour in which the noise created by the partisan home supporters was far more impressive than anything their players produced on the pitch.

Arsenal, though, found themselves a goal behind from the first decent chance CSKA created. The damage was done on the Arsenal right, where Konstantin Kuchaev had too much space to deliver a cross that was met by the head of Nababkin, who towered above Nacho Monreal. Cech, diving low to his right, managed to keep the effort out but Chalov reacted to the loose ball quicker than Shkodran Mustafi and stabbed it home from a couple of yards.

Suddenly Arsenal had a game on their hands. Kristijan Bistrovic’s rising first-time shot from just outside the area flashed past an upright and within five minutes of the restart the home team had a second. It was a desperately poor goal to concede in so many respects and started with Ramsey giving the ball away inside his own half.

The influential Aleksandr Golovin picked up possession a couple of passes later and with no Arsenal player attempting to close him down, the midfielder accepted the invitation to shoot from 30 yards. Cech was well-positioned to make the save but the Arsenal goalkeeper made a pig’s ear of things and succeeded only in parrying the ball into the path of Nababkin, who swept home emphatically.

Golovin’s free-kick was turned around a post by Cech moments later and Arsenal were on the rack, prompting Wenger to replace Jack Wilshere, who picked up a slight ankle injury, with Calum Chambers. Though he gave them another body in defence, it was a moment of inspiration from Welbeck that provided Arsenal with respite. A lovely exchange with Mohamed Elneny was followed by a coolly taken finish from the in-form forward, who has now scored five goals in as many games. Ramsey, running on to another Elneny pass, then completed the fightback.