With leaders Juve losing 1-0 at AS Roma on Saturday, second-placed Napoli were looking to up the pressure on their Turin rivals and bounce back after a 3-0 Europa League defeat at the San Paolo against Viktoria Plzen on Thursday.
After a minute's silence to remember former Napoli player Carmelo Imbriani, who died of cancer on Friday at 37, it was the visitors who came out in determined mood with Gianluca Sansone going close early on.
Napoli responded well though, with Lorenzo Insigne letting fly from distance and Edinson Cavani then failing to capitalise on some good movement, fluffing a shot while off-balance into the arms of grateful goalkeeper Sergio Romero.
Samp's big chance to break the deadlock came just after the half-hour mark when Napoli keeper Morgan De Sanctis tipped a low drive from Sansone past the post, then flapped at the resulting corner only to be bailed out by Valon Behrami, who cleared off the line.
Behrami was at it again after the break, this time with a decisive block to deny Mauro Icardi's shot on the notoriously bad San Paolo pitch.
Napoli were living rather dangerously but, as the game entered its final phase, the visitors were clearly tiring.
Goran Pandev came off the bench to link up nicely with Marek Hamsik, whose powerful left-foot shot was only kept out by a full-stretch Romero.
Napoli were beginning to assert themselves, with Paolo Cannavaro coming out of defence to test Romero with a decent effort, but struggled to make possession count in front of an increasingly impatient crowd.
Juventus still remain within touching distance, albeit four rather than two points away, with the two sides meeting at the San Paolo in March.
Napoli coach Walter Mazzarri did not speak to the press afterwards but sporting director Riccardo Bigon said this was because of illness.
"We remain convinced that we have our future in our hands. "We created plenty of chances against Sampdoria, we're still optimistic about our chances in this title race," Bigon said.
"Mazzarri? He's not well. He's got a 38-degree temperature, he's gone home to get some rest."
Sampdoria coach Delio Rossi was serving a touchline ban following an altercation with Roma players last weekend.
His right-hand man Fedele Limone was satisfied with a well-earned point.
"We worked really hard defensively, we gave very little away to Napoli," the assistant coach said. "The pitch? It's the same for everybody. It was a problem for us when it came to trying to find space, it certainly did affect us."
Struggling Pescara lost 2-0 to Cagliari while Torino earned a useful three points with a 2-1 win at home to Atalanta.
Genoa, easing themselves clear of the drop zone, saw off Udinese 1-0 and Catania are seventh thanks to a 1-0 defeat of Bologna.
Fifth-placed Inter Milan play Fiorentina in sixth later on Sunday while Siena host Lazio on Monday.