As the game ran past 90 minutes, Allegri wasted time by juggling the ball rather than putting it straight back in play. It earned a furious response from Lavezzi, who kicked it straight at him and was sent off.
"It was a moment of tension when the game was basically over. He had this reaction and that was the end of it, but in those 30 extra seconds of stoppages Napoli scored the goal," said Allegri.
"If I made a mistake in dealing with the ball that way, then I apologise, but there was a ball boy throwing another sphere on to the pitch at the same moment.
"In Cagliari we always try to keep the ball on the field until the very end, whereas in some stadiums they disappear. We are an educated and respectful club, the Cagliari crowd should be happy to have a team like this."