Napoli effectively gifted the Serie A title to Juventus with a deflating 2-2 draw against Torino, which leaves them six points adrift with two matches remaining.
The visitors struck two second-half equalisers to deny Maurizio Sarri's men the victory they desperately needed to apply any sense of pressure in the race for the Scudetto.
Juve now require only a point - and, most likely, not even that given their vastly superior goal difference - to guarantee they finish first.
Marek Hamsik appeared set to be Napoli's hero on Sunday when he thundered in a stunning 100th goal in Serie A from just outside the area less than two minutes after stepping off the bench.
That gave Napoli a lead to protect over the remaining 19 minutes but they failed to hold on, instead folding under the tension that had appeared to affect them during last weekend's costly 3-0 defeat at Fiorentina.
Lorenzo De Silvestri proved the man to deny them on this occasion as he headed in Adem Ljajic's dipping cross seven minutes from time.
Ljajic's pass had earlier supplied Torino's initial equaliser 10 minutes after the interval, Daniele Baselli beating Pepe Reina with a deflected strike that cancelled out Dries Mertens' soft 25th-minute opener.
The Partenopei now seem set for a meek surrender in a title race that was well and truly alive courtesy of their memorable 1-0 win in Turin just two weeks ago and it could prove a disappointing ending to Maurizio Sarri's time in charge, with president Aurelio De Laurentiis admitting the coach could leave at the end of the season as has been heavily reported.
For their part, the players seemed well aware of the need to pursue three points at Stadio San Paolo as they took the initiative from the outset, with Lorenzo Insigne looking particularly dangerous.
The opener, though, was gift wrapped for birthday boy Mertens. Nicolas Burdisso collected Kevin Bonifazi's square pass with a heavy backwards touch and compounded it with a poor second that enabled Mertens to nip in and poke past the static Salvatore Sirigu at close range.
4 - Dries Mertens is the player that scored the most Serie A goals in the day of his birthday (four). Gift. May 6, 2018
Buoyed by the end of an eight-game barren streak, the Belgium international almost punished another cheap concession of possession shortly before the break, but Sirigu was this time up to keeping out the hurried shot.
Torino, who had been relatively secure either side of those nervy moments, were level within 10 minutes of the restart as Ljajic fed a pass into the feet of midfielder Baselli, whose left-footed effort from just inside the area deflected off Vlad Chiriches and beat Reina inside his near post.
Suddenly enthused, Torino next saw M'Baye Niang fire into the side-netting as Napoli appeared rattled by the swift change in circumstances.
Sarri turned to his bench and found inspiration in the shape of Arkadiusz Milik and goal-scorer Hamsik. Poland international Milik first thundered a strike against the left post before Hamisk went one better, thumping a stunning half-volley from just beyond the box that bent around the helpless Sirigu.
100 - Marek Hamsik scored today his 100th goal in Serie A, after 394 games played. Milestone. May 6, 2018
Milik should have put the result beyond doubt with just over 10 minutes remaining, but somehow side-footed wide as Insigne waited to tap home Jose Callejon's low cross.
And the miss proved costly in the 83rd minute, De Silvestri meeting Ljajic's cross in behind a sleepy defence and nodding home.
Napoli had half-hearted appeals for a handball in the area waved away in stoppage time as their Scudetto ambitions evaporated, with Juve just about ready to start the celebrations of what appears destined to be a seventh successive triumph.
