The Polish centre-back was on the mark midway through the second period to foil the Azzurri in their bid to go level with Roma
The Granata captain headed home from a left-wing corner midway through the second period to rock the Champions League challenge of Rafael Benitez’s side, who now face a concerted challenge for third place after wins earlier in the day for Lazio and Fiorentina.
Torino pressed well in the early moments, but Josef Martinez blazed one glorious effort from a Bruno Peres cross into the crowd. An extravagant overhead kick by Fabio Quagliarella from another Peres centre was then parried away by Mariano Andujar with the referee simultaneously calling a halt for a foul by the former Napoli front man on Christian Maggio.
The best the visitors had to show for their possession before the break were a couple of long-range speculators from Jonathan de Guzman and Marek Hamsik, and things got no better for them after the interval with Jose Callejon hammering a volley well wide of goal from a half-cleared free-kick.
And while Benitez looked to inject positivity into his side by bringing on Manolo Gabbiadini for skipper Marek Hamsik, his side soon got caught out at the back.
Kalidou Koulibaly unnecessarily screwed a clearance from midway all the way back for a corner, and from the resulting set-piece Glik stooped to steer a header beyond the flat-footed Andujar for his fifth goal of the season.
Gonzalo Higuain could have equalised soon after from a left-wing cross but fired well over, and Gabbiadini then curled a wonderful free-kick effort onto the base of the post.
The Neapolitans then laid siege to the home side’s goal but could find no way through, meaning they head into next Sunday’s clash with Inter with only a two-point advantage over fourth-placed Lazio. Torino, meanwhile, move ahead of Inter, Milan and Palermo into eighth spot.