Napoli took a big step towards qualification for the knockout stages by dominating Villarreal in a 2-0 Champions League victory at the San Paolo stadium here on Tuesday.
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 in 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.
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," he 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."
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.
Visiting coach Juan Carlos Garrido felt the difference between the teams was the two mistakes for the goals, but he denied their Champions League hopes were over.
"We lost the game because of two inexplicable mistakes on our part," he said. "It's difficult to remember two such mistakes in one game and it will be three years before we see this kind of thing happening again.
"In a two-minute spell we had one defender slip in the area leaving a player alone and then another player lose the ball and give away a penalty.
"Apart from these two episodes we played well, but we suffered too big a penalty for the way we played.
"There are still four games and 12 points to play for."
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 did not 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 left-footed across goalkeeper Diego Lopez on 14 minutes.
Three minutes later it was 2-0 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.
Garrido seemed perturbed by Napoli's domination and on 33 minutes he 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.