Mancini said: "If you are a top player it is not important what system you use.
"If you don't understand a system like that, you cannot play for a top team."
Richards admitted the Premier League champions were uncomfortable with the three centre-back formation, saying they preferred to play 4-4-2.
The Italian added: "What Micah said is not important. He answered a question. I understand people want to write about it, but to me it doesn't matter.
"Maybe Micah doesn't know because it was his first game for two and-a-half months."