Gargano made the switch to Inter Milan on a season-long loan with a view to a permanent deal, but Cannavaro has told his side not to dwell on the exit of the Uruguayan.
"He was a very important player, and grew up with this group, however, he made his choice and was sincere and open in his reasons," said Cannavaro.
"Now let us look forward. Whoever wears this shirt knows that they must give their best. Playing in Naples is special, and those that are here have to be happy and motivated to win something important."
Life without Gargano starts for Napoli with a trip to Palermo on Sunday.