Manchester City earned a momentous reprieve in one competition last week but in the FA Cup semi-final at Wembley with only 90,000 empty seats as judge and jury, they could not escape their sentence.

The Court of Arbitration for Sport might have allowed them back into the Champions League for the next two seasons but Arsenal showed them no mercy here.

Their shock 2-0 victory was a triumph of uncharacteristic resilience in defence, led by a brilliant display from David Luiz, and of clinical finishing from Pierre-Emerick Aubameyang, who scored goals in each half to dump City out of the competition they won last year by trouncing Watford in the final.

Arsenal will play either Manchester United or Chelsea in the final on August 1.

It was also the most significant victory yet for Arsenal boss Mikel Arteta, who has only been in charge at the Emirates since December but is already effecting improvements in attitude and style. This one was a victory for the apprentice over his old master as Arteta plotted a way past his former boss, Pep Guardiola.

Arsenal are languishing in ninth place in the Premier League but suddenly their season has new life. They beat champions Liverpool on Wednesday and this result stunned English football. City were widely expected to win this match and claim the FA Cup as their consolation prize for losing the Premier League but they spurned chance after chance and never looked at their best. 

City will now be able to pour everything into their pursuit of the Champions League but if they show the same vulnerability at the back in the second leg of their second round match against Real Madrid as they did here against Arsenal, the Spanish champions will fancy their chances of overhauling their first leg deficit. Overwhelmed by Liverpool in the league, this defeat was a rude shock for Guardiola and his team.

The empty stadium seemed particularly stark here. FA Cup semi-final day is usually a riot of colour and a feast of fan expectation and nerves. It is a day out as much as a football match, a day to dream of the final and sing about putting the champagne on ice. Not this time. Not now. Here, there were groundsmen forking the pitch and music echoing around an empty Wembley. It is a necessary measure for now but that does not stop it feeling all wrong.

Even with nine substitutes, Arteta could not find any room for either Mesut Ozil or Matteo Guendouzi in his squad. It is starting to feel increasingly likely that neither will be at the club next season, although finding someone to pay Ozil’s wages has always been put forward as the biggest stumbling block to the Germany midfielder moving on.

Arteta stayed true to the same system he had used in Wednesday’s victory over champions Liverpool at the Emirates and lined up with Kieran Tierney on the left side of a back three. It is the system that seems to get the best out of David Luiz – or do most to protect him, depending on your point of view – and after some heart-stopping early exchanges, Arsenal used it well.

Arsenal nearly handed City an early lead in the ninth minute with the kind of comedy defending that has become one of their hallmarks. Luiz played the ball square across his own box to Shkodran Mustafi who tried to step inside Raheem Sterling as Sterling closed him down. It had trouble written all over it.

Sterling dispossessed Mustafi easily six yards out and it appeared Arsenal were about to be severely embarrassed. Sterling tried to play the ball inside to give Gabriel Jesus a tap-in but Mustafi’s blushes were spared when the pass was intercepted and the danger cleared. It felt already as if Arsenal were in for a long evening.

Arteta’s side were starved of possession and defending with a degree of desperation. Kevin de Bruyne floated a ball to the back post, Riyad Mahrez nodded it back across goal and it was hacked clear before City could apply the finishing touch. By then, Kieran Tierney had already had to make a separate last-ditch clearance.

But after quarter of an hour, Arsenal should have taken the lead. Luiz has been roundly criticised since the restart but he received a ringing endorsement from Pep Guardiola last week when the City manager said he laughed when he heard pundits dismissing his talent. On cue, Luiz intercepted a long ball forward, chested it down, and played a slide-rule pass through to Aubameyang. Aubameyang was clean through but he hit his shot straight at Ederson, who saved it easily.

City did not learn from their escape though. A minute later, at the end of an 18-pass move that had started in Arsenal’s area and included ten players, Nicolas Pepe curled a ball across the City box to the back post. Aubameyang drifted away from Kyle Walker and met the ball as it dropped, clipping a right-footed half-volley past Ederson from a difficult angle. The keeper had no chance and the ball went in off the far post.

It was a brilliant finish to a superb move. It is easy to mock Arsenal’s talent for self-destruction but the goal was crafted from the courage to stick to their plan of playing the ball out from the back and beating the City press. Even though they had nearly come unstuck earlier, this time they had the skill and the confidence to work it perfectly.