Victory away at Juve looked to have given Napoli the opportunity to push all the way for a first Scudetto since 1990, but a failure to win either of the subsequent two matches put paid to their challenge.
And so, with Juventus drawing at Roma, a dominant Napoli display at the Stadio Luigi Ferraris counted for little, despite a marvellous strike from substitute Arkadiusz Milik just 75 seconds after his introduction that was followed by a Raul Albiol header.
The Partenopei had looked destined for a frustrating third winless game after Dries Mertens saw an early goal contentiously ruled out and Samp's debutant goalkeeper Vid Belec repeatedly denied Lorenzo Insigne.
But Maurizio Sarri and his men can draw encouragement from a 27th league win of the season, even amid talk the coach could depart in the coming weeks, having seemingly taken Napoli as far as he can.
Controversy has rarely been far away where Napoli are concerned during the run-in and a bizarre early call went against the visitors in this one.
Mertens was flagged as he stood in an offside position when finishing smartly following a corner, yet home defender Joachim Andersen appeared to have nodded the ball his way. However, the VAR ruled in Sampdoria's favour, much to the forward's disbelief.
Napoli kept up the pressure, though, and Belec awkwardly parried Insigne's curler over the top, before making a rather more accomplished stop from an Albiol header.
Another unorthodox save followed to keep Piotr Zielinski out and Insigne again cut in from the left to send an effort whistling past the far post.
Gianmarco Ferrari nodded against the crossbar at the other end shortly before the break, but Napoli were back on top following the restart and Insigne again went close.
Although chances arrived with less regularity and Belec blocked superbly when Insigne was able to wriggle free in the area, Milik made an instant impact.
Dipping onto his left foot around 20 yards from goal, the Napoli forward curled a majestic strike up and past Belec to ensure that Napoli would at least force Juventus to get a result.
That they did, though, and only personal pride was secured as Sarri's side added to their lead through Albiol in the final 10 minutes.
Key Opta stats:
- Napoli have picked up 88 points so far, their record in the top-flight.
- Arkadiusz Milik has scored the fastest goal from a Napoli substitute in this Serie A campaign (1 minute and 15 seconds).
- Vid Belec made seven saves in the match, his most since September 2017 - when he was playing for Benevento - vs Napoli (eight).
- Jorginho reached 150 appearances in Serie A in this match.