Napoli played out a toothless goalless draw with Dynamo Kiev, who were knocked out of the Champions League as a result of Wednesday's stalemate at Stadio San Paolo.
Besiktas' stunning fightback in a 3-3 draw against Benfica earlier on Wednesday meant that Napoli could not have progressed from Group B before the final round of pool matches even with a win.
However, Maurizio Sarri's men will still feel they missed a chance to pick up a big three points on their own turf.
Napoli, who have won just three of their last 10 in all competitions, now head into their final group game with everything to play for, knowing a point at Benfica will be enough to progress but only a victory will guarantee first place.
The home side made a promising start and a crucial challenge from Rudko denied Dries Mertens a shot at an open goal, before the Ukrainian blocked Jose Callejon's stab.
The hosts' momentum slowed as the first half wore on, but they came again after the break and Hamsik nodded Callejon's cross just beyond the far post.
Still Napoli came forward, though, and Rudko again held from Insigne, before diving to his right to parry Hamsik's drive.
Substitute Manolo Gabbiadini's effort from the edge of the box flew wide of the post and Rudko then beat away an attempt from the same man in a similar position.
Kalidou Koulibaly also headed over, but the hosts' desperate attempts counted for little and they face a crucial trip to Lisbon on matchday six.
