Tevez has been out with a hamstring injury for almost four weeks and is virtually certain to miss Saturday's trip to Everton.
"It is very difficult for him to play against Everton and if he doesn't play against Tottenham, it will be impossible for Carlos to play in the final," said Mancini.
Micah Richards could be on the bench at Goodison Park as he continues to make progress after a hamstring injury.
"Micah is very close," said Mancini.
The City chief was also unconcerned about Bayern Munich's interest in Germany defender Jerome Boateng.
Mancini is the first to admit Boateng's first season at Eastlands has been difficult but the Italian is adamant the former Hamburg star's future remains with City.
"I am happy Bayern have said this because it proves we signed a big player," said Mancini. "Jerome has had many problems this year, including three or four injuries.
"But he will be staying here. He is a big part of our future.
"If he doesn't have any problems next year, Jerome can be one of the best defenders in Europe."
Source: PA
Source: PA