Kompany was given his marching orders 12 minutes into the match after a two-footed lunge which was deemed dangerous by referee Chris Foy, despite making no contact with United winger Nani. City went on to lose the match 3-2 after a spirited second-half comeback.
Mancini was incensed by Foy’s decision to send off his captain, and after the match suggested the referee had only awarded a straight red card after being convinced by an appeal from Rooney.
"Rooney told [Foy] his decision,” the Italian told reporters. “He influenced the referee. [Rooney] was near the referee. Yes [he influenced the decision]."
Kompany now faces an automatic four-match ban after picking up his second straight red card of the season – a punishment Mancini confirmed City will appeal against.
“I don’t think it was a red card, we will appeal and I hope we win the appeal,” he told the club’s official website.
Despite his anger at the dismissal of his captain, Mancini insisted his side’s second-half display, which saw them come back from 3-0 down to 3-2 and almost equalise late on, has left him more convinced than ever that they have what it takes to win the Premier League.
“Of course I am disappointed that we have lost the game and gone out of the FA Cup but I was pleased that we played such a good game and I am proud of my players,” he added.
“The players have shown character and taken a step forward. I think more than ever that we can go on and win the league.
“If we show the same attitude and strength in other games that we showed against United with only ten men then yes we can win the league.
“I said we had to improve and I think we are doing so.
“To play 80 minutes against one of the best teams in Europe with 10 men and come so close to saving the game was fantastic.”
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