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 dominated possession, but struggled to create clear openings as Yevhen Khacheridi and Domagoj Vida marshalled a speedy front-line superbly.
Dynamo goalkeeper Artur Rudko also weighed in with the occasional save, but a lack of attacking threat at the other meant they failed to keep their already slip hopes of reaching the last 16 alive.
Napoli, who have won just three of their past 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 clinch 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.
Lorenzo Insigne then stumbled as he bore down on goal and Marek Hamsik struck straight at Rudko from 20 yards, with Dynamo offering little in response.
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.
Insigne hit a curled effort that was gathered by Rudko at the second attempt, while some brave defending from the away side provided a platform for Serhiy Sydorchuk to lash over at the other end.
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 from a similar position.
As Napoli continued to rely on shots from distance in the hunt for an opener, Mertens became the latest man to push an effort past the post.
Kalidou Koulibaly also headed over, but the hosts' desperate attempts counted for little and they face a crucial trip to Lisbon on matchday six.