Vieira was dismissed after an aerial clash with Marco Materazzi and could now be handed a ban for the start of the Barclays Premier League season if the referee's report finds its way to the English FA in the coming days.
City assistant manager Brian Kidd said: "Patrick has gone for the ball. He genuinely didn't see the player. I know it's difficult for the referee but there was no intent there. Hopefully people will have a look at it and realise that it wasn't a genuine foul.
"But to be banned for the start of the season because of what we have seen tonight would be very harsh."