The Manchester City boss selected Mario Balotelli, Carlos Tevez and Edin Dzeko for the recent encounters with Aris and Fulham. Although the policy worked against Aris, as City cruised into the Europa League last 16, it did not in the Fulham encounter when Tevez and Dzeko failed to impress.
Mancini said: "At this moment I don't think we can play all three. The team is too tired."
He added: "Maybe when all the players have recovered and we have more options but as it presently stands, it is important we have proper balance."
Balotelli was given more responsibility against Aston Villa in the FA Cup and responded by bagging his 10th goal of the campaign, a magnificent half-volley after being sent through by Yaya Toure.
Mancini is sure when the 20-year-old gains some much-needed maturity, nothing is beyond him.
"I know him, Mario. I know what he is capable of," said Mancini.
"If he wanted to, he could score in every game. I wish he always played like he did against Villa because he did really well and scored a brilliant goal.
"In future he could definitely play as a central striker. He would be perfect in this position, although the truth is, a player with the technique of someone like Mario could play anywhere."