Milan: Goals by Jose Callejon and Dries Mertens handed Napoli a stunning 2-0 win over champions Juventus and sparked some life into the Serie A title race on Sunday.
Juventus had seen their 14-point lead cut back earlier in the day when Roma, in second with a game in hand, prevailed 2-0 at struggling Sassuolo.
Napoli came flying out the blocks and at the tail end of a dominant first half Callejon broke the deadlock in the 37th minute.
The pace slowed after the break but moments after replacing Marek Hamsik, Mertens made the most of Goran Pandev's delivery to beat Gianluigi Buffon with a crisp drive from the edge of the area and condemn Juventus to just their second league defeat of the season.
Juve now lead Roma by 11 points with Napoli, who have been chasing the second automatic Champions League qualifying spot, still third but six points behind Roma and 12 ahead of Fiorentina.
Napoli coach Rafael Benitez told Sky Sport Italia: "There's always little things we can improve on but on the whole we played really well, although I'd like to see this kind of concentration against the smaller teams as well.
"But the key to victory was ball possession. For Juve it was difficult to get back up the field without having the ball, although maintaining this kind of intensity over the whole season isn't easy."
Juve suffered their only other reverse in a 4-2 defeat away to Fiorentina in October.
Coach Antonio Conte said his side's Europa League commitments had perhaps made the difference.
"We didn't play well in the first half, although we improved somewhat in the second.
"But there are tired legs in my squad, that's inevitable when you've been playing every three days and are unable to rotate due to injuries."
Striker Gonzalo Higuain returned to the Napoli line-up after being rested for the 4-2 win at Catania in midweek, while Pablo Daniel Osvaldo replaced the suspended Carlos Tevez to partner Fernando Llorente in Juve's attack.
The statistics, however, were all in favour of Juventus, who were unbeaten in their last six encounters with Napoli and had restricted the hosts to only one goal in their last four games.
Napoli enjoyed the early pressure with Buffon pulling off a great reflex save in the seventh minute to stop Callejon from close range and the Spaniard tested the 'keeper again on the half hour when he picked up Lorenzo Insigne's cutback after it missed Higuain.
Juve were seeing little of Pepe Reina's goal and shortly before the interval Kwadwo Asamoah was caught out in a makeshift defensive role and Callejon ghosted in behind the Ghanaian midfielder to meet Lorenzo Insigne's cross to beat Buffon from close range.
At the other end a spectacular bicycle kick from Osvaldo was well over the bar.
Asamoah made way for Mauricio Isla eight minutes after the restart and the Chilean almost made the difference immediately when he controlled well on the right to cross for Osvaldo, but Reina got down low to block.
On the hour, Hamsik won a free kick when his feint prompted Leonardo Bonucci to foul on the edge of the area and once again Juve had Buffon to thank for tipping Faouzi Ghoulam's well-struck effort to safety.
Conte shook things up when he replaced Paul Pogba with Claudio Marchisio and minutes later Osvaldo made way for Mirko Vucinic.
Vucinic had to wait only moments before having a shot on goal when he collected Arturo Vidal's short pass on the edge of the area only to curl wide of Reina's upright.
With legs tiring, Higuain came off for Goran Pandev in the 73rd minute and Napoli had Ghoulam to thank when he ran back to block Isla as he teed up a shot to the right of goal following Vucinic's through ball.
At the other end Hamsik was sent through by Pandev but Buffon had no trouble getting low to block the Slovakian's tame shot from the edge of the area.