Reigning champions City fell 12 points behind crosstown rivals Manchester United following the weekend's 3-1 defeat at Southampton and now Mancini wants to ensure that only those willing to scrap for the club will be involved in the next few months.
"I am sure we will change that, because I will change players next week," he told the Manchester Evening New ahead of the FA Cup visit of Leeds United this coming weekend.
"I only want players who are ready for the fight in the last 12 games.
"I am very angry with a lot of my players, and very disappointed at the performance, because it is impossible to play the way we did.
"We didn't fight for every ball. We can't always win by playing well - that is normal. Sometimes we play well and win, but you also need to be able to win because you fight for every ball, and fight against an opponent who also wants to win the game.
"Every team that plays against us treats it like a Champions League final, but we should know this, it is normal.
"We now have 12 games left, need to do well in the Premier League, and we have the FA Cup - there are games left and we can do better. We need to finish the season the way we did last year."