Mancini said: "He's a defender. Sometimes when the defender is under pressure he can do a bad tackle but I think he needs to pay more attention, because this has happened two times.
"We can have a problem if we have another situation like this. I spoke with Vinny and told him to have more attention on his tackles."
The sending-off has since been overturned after City lodged an appeal with the Football Association, meaning that Kompany is available for Saturday's visit of Fulham.