Napoli forward Jose Callejon headed a late winner to hand Roma only their second defeat of the season on Sunday and dent the capital city side's scudetto challenge.
Roma travelled to the San Paolo hoping to reduce the arrears on Juventus after Antonio Conte's side had stretched their lead to 14 points with an earlier 1-0 win over fourth-placed Fiorentina.
However Rudi Garcia's men missed a host of chances and were punished in the 81st minute when Callejon rose to meet Faouzi Ghoulam's cross from deep on the left to beat Morgan De Sanctis with a precision header.
Juve sit top of the pile with a 14-point lead although Roma, who remain second, have a game in hand after a recent fixture at home to Parma was rained off.
Napoli coach Rafael Benitez said in midweek their title bid was virtually over, but their 16th win of the campaign has put them back in the fight for the runners-up spot which offers an automatic Champions League place.
"It was a high-octane game, they had their chances and we had ours, but we managed to score," the Spaniard told Sky Sport.
Callejon was less effusive about the significance of the win: "Now, our aim is second place.
"If you were looking for character and determination, we showed it out there."
Roma suffered a blow before the quarter hour when Kevin Strootman, who had injured his right knee playing for Holland against France in midweek, was carted off with a fresh injury to his right knee.
While Garcia will be hoping the Dutchman emerges with good news following tests on Monday, he admitted: "Thanks to our pace we managed to create quite a few chances.
"Unfortunately, none of ours went in. To score, you also need a little luck.
"We didn't deserve to lose, but that's football. It's not always the strongest who wins."
Roma made light of Strootman's setback but ultimately failed to capitalise on a largely dominant first half in which Gervinho and Radja Nainggolan both tested Pepe Reina.
Roma had the ball in the net on 26 minutes when Mehdi Benatia headed Alessandro Florenzi's free kick from the left past a static Reina, but the Moroccan was among three players who had strayed offside.
- Desperate block -
Moments later Miralem Pjanic's pass found Gervinho unmarked on the left of the area but after deftly rounding his marker the striker's shot was closed down by the onrushing Reina.
Gervinho found more space on the left five minutes from the interval but after a give and go with Florenzi the Ivorian was stopped in his tracks.
Roma were edging closer to breaking the deadlock and when Gervinho was closed down to the right of goal he laid off for Michel Bastos, whose shot forced Reina to fingertip over.
Napoli's chances up until then had been restricted to Gonzalo Higuain's angled drive which sailed well wide.
But on the cusp of half-time Dries Mertens skipped around Maicon to force De Sanctis into a desperate block.
The Belgian tested De Sanctis from even further out five minutes after the restart but his effort sailed just over with the 'keeper at full stretch.
Napoli were clearly on the ascendancy and should have broken the deadlock two minutes later when Pjanic gave up possession to Higuain, who forged ahead to set up Callejon on the right only for De Sanctis to rush out and block the Spaniard.
Higuain fired a half-volley just over De Sanctis's bar from Lorenzo Insigne's cut-back moments later, but Roma had not given up.
Maicon's shot from Gervinho's cut-back on the right of the area had Reina scrambling to save after it took a slight deflection and then Florenzi glanced a header wide from Maicon's deft cross with the outside of his boot.
Roma's misses, however, proved costly when Alessio Romagnoli fatally gave Callejon enough space in front of goal to rise unhindered and head Ghoulam's precision cross past De Sanctis.
Earlier, a first-half strike from Juventus winger Kwadwo Asamoah secured a the champions' 1-0 win which allowed Conte to finally talk about the title.
"We've got one hand on the trophy," said the Juve handler.