The City skipper was shown a straight red for an apparent two-footed lunge on Jack Wilshere, which came well after referee Mike Dean had earlier dismissed Arsenal defender Laurent Koscielny for a foul on Edin Dzeko.
The Premier League champions ran out comfortable 2-0 winners, but the result was tarnished by Kompany’s dismissal, which could lead to a three-game ban, and Mancini confirmed the club will be asking the FA to overturn the result.
”This is not a red card, absolutely not," Mancini told Sky Sports. "He has one foot to take the ball, the other is left. I think that the referee made a mistake there.
“It was not a sending off for Vinnie, because Vinnie took the ball with only one foot after anticipating the opponent.”
Mancini admitted the earlier red card for Koscielny, who hauled down Dzeko in the area, made things easier for his side, but he was disappointed the Citizens were unable to extend their lead after the break.
"If you play with 10 players it is very difficult," Mancini said. "But we started the game very well, we played high, pressed high. After the sending off it was easier. Second half we were too soft and we missed three or four goals and after the game can be open."
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