Mancini now believes Tevez's position at the club is untenable.
Asked if Tevez was finished at City, Mancini said: "I don't decide this, but if I did, then yes. I helped Carlos for two years but I cannot accept this behaviour."
Mancini is clearly fuming and it is difficult to see how there can be any way back for the 27-year-old now.
"He just refused to go on. I don't know why," said Mancini.
"I am the manager. I decide everything. I have helped him every time for two years, he has wanted to leave but I still picked him.
"The thing is there were still 30 minutes until the end of the game. We could still change it.
"Carlos didn't play at the start of the season because he has not had a pre-season for three years. He was not ready to play.
"If it was another player may be this could happen but for a player to refuse to go on in an important game like this is not right."