The hosts were dominant throughout the game and could have scored a lot more against Ivo Pulga's toothless charges in the Stadio San Paolo
Rafael Benitez's side approached the match at the San Paolo fresh from Saturday's 3-1 win over Fiorentina in the cup final, but there were no signs of a hangover as Dries Mertens, Goran Pandev and Blerim Dzemaili were on target to ensure they took all three points from a toothless Cagliari.
Napoli were on top throughout the game, with very little fight from their opponents. The home team fired 27 shots towards Marco Silvestri's goal, with Cagliari returning four, only two of which were on target.
The game got off to a bright start with Napoli creating the first real chance of the game, creating much confusion in the Cagliari box as Mertens, Callejon and Pandev had a chance each but the chance soon faded.
From then on, however, it was quite slow, as Benitez's men dominated possession without really doing much with it.
The hosts' next opportunity came in 28 minutes when Dzemaili fired towards goal from 25 yards. The movement of the ball in mid-air made it a difficult one for Silvestri to read but he reacted quickly enough to palm it wide. After the resultant corner, Dzemaili took the ball in from the right and fired low to the keeper's left but he got down on time to keep it out.
Despite their dominance, the Partenopei required a penalty to break the deadlock in the 33rd minute as Pandev took on a pass and turned past Daniele Conti but was pulled down by the defender and the referee was quick to point to the spot. Mertens then stepped up to smash it into the bottom corner from 12 yards.
Benitez's side's lead was extended shortly before half-time when Cagliari failed to clear a Marek Hamsik flick and it landed perfectly for Jose Callejon who squared to Pandev and the Macedonian slid in to knock it home from close range.
As if things weren't easy enough for Napoli, they soon found themselves with a further advantage as Silvestri was sent off with a straight red card just eight minutes after the restart for bringing Pandev down inside the box. And this time it was Hamsik who took the penalty, but he smashed it off the bar.
As Cagliari attacked in the 57th minute looking to restore some pride, they were duly punished as the home side stole the ball and burst forward with five attackers charging towards their opponents' danger area. Pandev fired the first shot which was saved by Agim Ibraimi but Dzemaili was there to scoop in the rebound.
Substitute Duvan Zapata should have made it 4-0 to Napoli as Hamsik nodded on to Mertens down the left wing who moved it across to the Colombian but a deflection prevented him from steering it in.