The Bavarian side almost let a three-goal lead slip, but the 66-year-old insists that his side did not lack caution against the visiting Italians at the Allianz Arena
The Bundesliga leaders raced into a three-goal lead courtesy of a first half hat-trick from Mario Gomez, but a brace from Federico Fernandez ensured a nervy end to the clash.
Speaking at a press conference in the wake of the game, Heynckes maintains that even at 3-0, Napoli were never out of the game.
"There is no way we were careless after we went 3-0 up," he said. "I told the team before the game that it would be very difficult today.
"Napoli never gave up, they have superb morale and are the top when it comes to fighting and running.
"At this level, you get nothing for free and until today they had not lost a single Champions League game. We have to be pleased that we won. Such games happen in Europe, maybe this will help bring expectations back down to earth." Heynckes said.
Meanwhile, Heynckes voiced his hope that his team can recover from the news that Bastian Schweinsteiger will miss up to six weeks with a collarbone injury.
"We've always been able to replace injured players," he said. "I hope that we also succeed this time."