For Arsenal, it had to be from a corner and after the week that had gone, it had to be Leandro Trossard who made the difference. The fall-out from last Sunday’s explosive 2-2 draw at Manchester City had raged, a prominent talking point, the moment which shaped Arsenal’s darkly impressive rearguard action being Trossard’s second yellow card for kicking the ball away. Here, he rescued his team.

It looked like being a story of Arsenal throwing away two points from a winning position for the third time this season. That, and a sensational second-half goalscoring cameo by the Leicester right-back, James Justin, plus the defiance of the goalkeeper, Mads Hermansen.

Related: ‘I love and respect Pep’: Arteta tries to defuse row with Manchester City rival

Having made it 2-1 with a deflected header, Justin produced a volley of irresistible sweetness to equalise. Hermansen made 13 saves – the most in a Premier League game since David de Gea for Manchester United here against Arsenal in 2017.

Arsenal’s total dominance of the first half, which had taken in goals from Gabriel Martinelli and Trossard looked set to count for little, especially as they could not find a way back through in regulation time.

Enter Trossard. There were 94 minutes on the clock when Bukayo Saka sent across a deep corner and there was Trossard, the man over that Arsenal always seem to have beyond the far post in these situations, to guide a volley towards goal. It took a heavy deflection off Wilfred Ndidi to beat Hermansen and Arsenal were on their way to taking advantage of City’s draw at Newcastle earlier in the day.

There would be a twist from the narrative-hating dubious goals committee which ruled that it had to go down as an Ndidi own goal. But this was about the composure of Trossard and, more generally, Arsenal refusing to feel sorry for themselves after Justin’s intervention; about finding a way.

Kai Havertz would make it 4-2 at the very end after a Justin clearance hit him and went in and it added up to a deserved victory for Arsenal, even if they needed to go through the wringer to secure it.

The drama felt like a distant prospect at half-time. Justin had rushed up the inside right in early running to see a shot blocked by Riccardo Calafiori but it would be an extremely isolated first-half foray from Leicester.

Arsenal brought the intensity, winning the duels – especially William Saliba versus Jamie Vardy – sparking quick transitions. Saka was in the mood and Martinelli might have had a hat-trick inside 25 minutes. The chance he did take was made by Saka and Jurrien Timber up the right, the latter cutting the ball back. Martinelli’s finish on the spin was marked by precision.

Steve Cooper was booked for complaining about a challenge by Saliba on Vardy in the build-up and the Leicester manager also raged when Riccardo Calafiori was spared a second yellow card in the 70th minute for a foul on Facundo Buonanotte. “Two really, really poor decisions,” he said. Against that, Oliver Skipp was fortunate to escape a second booking on 83 minutes for a late tackle on Saka.

Arsenal poured forward in waves. Havertz sent a downward header just wide and when Trossard opened up his body to sidefoot a Martinelli pull-back into the far corner, it looked almost too straightforward for Arsenal.

Leicester appeared beaten. And yet they would revive in stunning fashion after the interval with a goal that said plenty about their fighting spirit. Buonanotte dropped in a free-kick and when Justin headed goalwards, the ball flicked off Havertz to deceive David Raya.

Arsenal pushed and Hermansen excelled, particularly when making a double save after a corner to keep out headers from Gabriel Magalhães and Calafiori. Timber blasted high on the third phase. Arsenal went close again when Trossard jabbed against the outside of a post.

But Leicester hinted at the equaliser. It was not so outlandish when it came, just spectacular. Buonanotte had twice gone close and Arsenal were looking slightly open. Justin might never hit a cleaner strike, the technique sumptuous as he cut across Ndidi’s deep cross with the outside of his right foot to send the ball screaming in off the far post.

Arsenal did not panic. They came again, creating chances and yet Hermansen was having one of the games of his life. Even when he erred with a loose pass, playing out straight to Declan Rice, he redeemed himself with a save from Trossard.

Hermansen had saved brilliantly to keep out a Havertz volley and there was more from him – a push away to deny the fearless Arsenal substitute, Ethan Nwaneri, and a tip over when Calafiori climbed to reach a Saka corner. Hermansen’s resistance and that of Leicester would be broken at the death.