It means the Italians trail Group A leaders Bayern Munich by two points after two games but crucially they are respectively three and four points ahead of Manchester City and Villarreal on their debut in the competition under its current format.
Marek Hamsik opened the scoring and Edinson Cavani added a penalty inside the first 17 minutes in a first period controlled by the hosts. Villarreal livened up a little after the break, but failed to create many clear-cut chances and their second-round hopes are hanging by a thread after earning no points from their first two matches.
Napoli coach Walter Mazzarri said that, but for tiredness, his players could have secured a more emphatic victory.
“The players knew that with a third goal there would have been no way back and they did take the risk of trying to get the third on the counter,” Mazzarri said. “We messed up our chances on the counter, but we were tired and our energy levels dipped. We’ve been playing a lot recently and given the way we play, we use more energy than the others and we pay for that.”
Former Udinese defender Cristian Zapata shot wide for the visitors early on after a bit of pin-ball in the box. But Napoli soon took the game by the scruff of the neck and after Cavani’s shot was blocked, Ezequiel Lavezzi fired just over.
They didn’t have to wait long, though, to go in front as Lavezzi’s cross found Hamsik lurking at the back post. Aided by a defender’s slip he had time to take the ball down on his chest and rifle home across goalkeeper Diego Lopez on 14 minutes.
Three minutes later it was two as Lavezzi out-paced Gonzalo Rodriguez in the box before the defender went to ground and was adjudged to have brought down the marauding Argentine. Cavani stepped up to fire the resulting penalty low to Lopez’s right.
Nilmar had a half-chance for the visitors but fired straight at Morgan De Sanctis. Just past the half hour mark Cavani almost gifted Villarreal a route back into the game with a back pass only a striker could play, but although Nilmar beat De Sanctis to the ball, he guided his first-time effort wide.
The visitors’ coach Juan Carlos Garrido seemed perturbed by Napoli’s domination and on 33 minutes replaced the ponderous Rodriguez with winger Javier Camunas. Villarreal came out with a little more purpose after the break and a Camunas cross found Italy striker Giuseppe Rossi’s head, but his effort lacked the power and angle needed to beat De Sanctis.
Jonathan De Guzman had a couple of free-kicks around the box but failed to get either past the wall.