Balotelli was pictured scuffling with Richards as tempers flared in a training session on Thursday, attracting a fresh round of tabloid headlines.
However Mancini is relaxed about the latest off-the-field incident involving Balotelli, who famously unveiled a t-shirt with the slogan "Why Always Me?" after scoring in the 6-1 rout of Manchester United in October.
"I asked him, 'Why always you?'" Mancini said.
"He said it was because he didn't pass the ball to him. It was a really stupid thing, it was nothing. After 10 minutes it was finished.
"When you play a match eight versus eight and you are passionate, it can happen with every team. Not every week, but often.
"Mario and Micah were boxing, but they are like twins. They are very good friends.
"This has happened with Mario four times now - he is the king for this. But it has happened with other players.
"However, Mario should pay attention, not just about this, but in every situation.
"We are near Christmas, at the end of the year it is a very dangerous time for fireworks. It is better he stays in the hotel!"
Balotelli has been living in a Manchester city centre luxury hotel after an incident at his home in October when fireworks were set off in his bathroom.