Mancini turned to Tevez in the second half of City's European match at the Allianz Arena as his side trailed 2-0 following a first-half brace from Bayern forward Mario Gomez.
But, speaking after the defeat, the Italian coach has said Tevez, who was linked with a move away from the club in the summer although a transfer failed to materialise, would not enter the fray when Mancini looked to alter City's fortunes.
Mancini said: "He just refused to go on. I don't know why. I cannot be happy with this situation. Would something like this happen at Bayern Munich, AC Milan or Manchester United? 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 maybe this could happen but for a player to refuse to go on in an important game like this is not right."
When asked if he had any explanation for Tevez's behaviour, Mancini said: "It is impossible. I asked him to go in and help with the team. We have 11 players. Maybe he was disappointed because he didn't play (from the start)."
City boss Mancini went as far as to suggest Tevez, who left Manchester United for City in 2009, will not play for the club again. Mancini said: "If I have my way he will be out of the club.''
Pressed further on 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.''
Tevez, speaking through an interpreter, gave little away. In an interview with Sky Sports News he said: "I have been professional during all my time here. Last season I was the top scorer and I wanted to leave for family reasons - but I keep trying to do my best.''
The mood contrasted starkly with Bayern who are top of the group with six points from two games thanks to victory courtesy of two goals by Mario Gomez.
After a good opening by City, the Bundesliga leaders took control and were ultimately good value for their victory. Manager Jupp Heynckes said: "We chose the right time to score and then played very confidently.
"At the beginning of the game we were nervous and we did not do ourselves justice. We changed midway through the first half and came into the game. Franck Ribery has given a world-class performance, Bastian Schweinsteiger also.
"In the second half we played as a unified team. At the moment we have not only a great team spirit, but also act in harmony, a good foundation and outstanding individuals.''
Chairman Karl-Heinz Rummenigge concurred, saying: "This was a very good game from us. Manchester City also played very well in the first 30 minutes to show that they are a strong team.
"We played mainly in the second half, totally in control. It was a great team performance, with Franck Ribery and Jerome Boateng playing really strong.''
Goalscorer Gomez said: "Manchester ran the ball well at the beginning. We were perhaps a little nervous, which is really inexplicable, because we are actually in a good phase. As a team we have from the 30th minute done well and ultimately deserved to win. I have not played outstanding, but scored two goals.''