Balotelli was dismissed for arguing with the referee at the end of Sunday's 2-1 home defeat and suspended the following day.
Milan have decided not to appeal against a three-match ban and he is sorry for letting the team down, although he did feel he should have been given more protection by the referee earlier in the game.
"I apologise to my team-mates, who train hard every day. I also apologise to the referee," he told Sky Sports Italia. "I reacted the wrong way to provocation.
"Mario has made a mistake. He has been provoked and made a mistake in reacting.
"If Mario makes a bad mistake, Mario should be punished. But against Napoli it was the same old story, the fouls against me didn't count for anything, I was the only one who could do anything wrong."