Stephan El Shaawary's early opener for Roma looked to have won the game for the visitors, but Belgian international Mertens pounced in the 90th minute to limit the damage for Napoli
Dries Mertens grabbed a late equaliser to snatch Napoli a 1-1 draw with Roma on Sunday which saw Carlo Ancelotti's men cut Juventus' lead at the top of Serie A to six points.
After seeing Paris Saint-Germain steal a last-gasp 2-2 in their midweek Champions League clash at the Parc des Princes, this time it was Napoli's turn to salvage a point at the death.
Stephan El Shaawary's early opener for Roma looked to have won the game for the visitors, but Belgian international Mertens pounced in the 90th minute to limit the damage for Napoli.
Reigning champions Juventus remain well clear after Cristiano Ronaldo scored a double, including a thunderous 25-yard winner, in a 2-1 win at Empoli on Saturday.
But last year's runners-up Napoli are now unbeaten in their last five games in all competitions since a 3-1 loss at Juve in September.
Just seconds after Edin Dzeko had seen a long-range shot fly narrowly wide, El Shaarawy gave Roma a 14th-minute lead with his third goal of the season.
Dzeko failed to get a touch on Turkish winger Cengiz Under's low cross, but the 26-year-old El Shaarawy was on hand to slot the ball in off the post, despite the best efforts of Kalidou Koulibaly on the line.
The hosts quickly went in search of an equaliser, but Roma goalkeeper Robin Olsen did well to deny both Arkadiusz Milik and Marek Hamsik in quick succession.
Napoli dominated possession in the second half, but struggled to create many clear-cut chances, with Mertens seeing two late efforts ruled out for offside.
But the 31-year-old winger latched onto a miskick from Jose Callejon to smash into the roof of the net and score his fifth goal of the campaign.
Earlier on Sunday, Gonzalo Higuain hit a crucial equaliser and Suso fired a second-half winner as AC Milan got back on track in Serie A with a 3-2 win over Sampdoria.
Coach Gennaro Gattuso was under intense pressure after a last-gasp derby loss to Inter last week was compounded by a 2-1 defeat by Real Betis in the Europa League on Thursday.
But the former Rangers and Milan midfielder has won respite, for the moment at least, after a fourth league win in nine outings left Milan fifth, albeit 13 points adrift of leaders and champions Juventus.
"Tension is normal when you lose to Inter and then in the Europa League," Gattuso told Sky Sport Italia.
"I asked to see 23 rabid dogs today and we added quality to that too. You can't beat Sampdoria only with grit and we put three goals past them. It was a wonderful game."
📸 Time to relive the game: scroll through our photo gallery of the match 👉🏻https://t.co/giSFymPfoP— AC Milan (@acmilan) October 28, 2018
📸 Rivivi la vittoria dei rossoneri: guarda la gallery di #MilanSampdoria 👉🏻 https://t.co/p7eH1N1rRC pic.twitter.com/q2BGM4ARZo
Milan looked to be under the cosh when Sampdoria took a 2-1 lead through Fabio Quagliarella on 31 minutes after Riccardo Saponara had levelled Patrick Cutrone's 17th-minute opener for the San Siro giants.
But Higuain responded on 36 minutes and, amid a second half that saw few real chances, Spanish forward Suso provided an impressive winner.
"I have to thank my players for a performance of character and quality," added Gattuso. "We've got to keep working, getting better and enjoying each others' company."
Sassuolo 2 (Marlon 17, KP Boateng 85-pen) Bologna 2 (Palacio 2, Mbaye 56)
Genoa 2 (Romulo 32-pen, Romero 67) Udinese 2 (Lasagna 65, De Paul 70)
Cagliari 2 (Pavoletti 15, Castro 59) Chievo 1 (Stepinski 79)
SPAL 0 Frosinone 3 (Chibsah 40, Ciano 53, Pinamonti 89)
AC Milan 3 (Cutrone 17, Higuain 36, Suso 62) Sampdoria 2 (Saponara 21, Quagliarella 31)
Napoli 1 (Mertens 90) Roma 1 (El Shaarawy 14)