The Italian was taken off for Sergio Agüero in the 56th minute after an indifferent display during City's 3-0 win against Sunderland. Balotelli did not make any eye contact with his manager, Roberto Mancini, as he headed for the dressing room.
David Platt, the assistant manager, added: "I don't know why he did that. He doesn't normally."
Balotelli flew home to join up with his national squad in Italy immediately after the match, but is not expected to be disciplined.
After the win, Mancini said: "I am happy with Mario, he played a good game."
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