The title rivals played out a fierce 2-2 draw at the Etihad with Pep Guardiola's men rescuing a point through John Stones deep into injury time.
Erling Haaland gave the champions an early lead but the Gunners hit back through goals from Riccardo Calafiori and Gabriel in an action-packed first half.
And there was more action to come as Trossard was shown a second yellow card for kicking the ball away in the dying minutes.
The Belgian fouled Bernardo Silva in the eighth minute of first-half added time before hoofing the ball clear.
Leandro Trossard was sent off during Arsenal's 2-2 draw with Manchester City on Sunday
Referee Michael Oliver had already blown his whistle for the foul and was convinced that Trossard had been deliberately trying to delay the restart - something officials were told to clamp down during pre-season briefings.
However, The Mirror report that Trossard told his team-mates that he never heard Oliver's whistle and that is what he told the official during the his protests.
The incident came just weeks after Declan Rice was shown a highly controversial red card against Brighton for the same offence.
And Sky Sports pundits Jamie Carragher and Gary Neville both agreed that Trossard knew what he was doing.
Carragher said: 'There's no doubt he's heard the whistle but it comes so quickly after the whistle it means he can get away with it. But he knows what he's doing.'
Neville added: 'The reason he (Oliver) knows he's heard the whistle is because he's half pulled out of kicking it away. He doesn't go fully through it.'
Carragher continued: 'what is he doing? The position his team find themselves in, and how pivotal these games are when you're looking at points totals at the end of the season. Ridiculous thing to do.'
Arsenal manager Mikel Arteta was visibly furious with the decision to dismiss Trossard.
However, he aimed his frustration at the officials, rather than his player, and he and his coaching staff embraced Trossard as he trudged off the field.