Juventus suffered a major setback in their quest to win a tenth successive league title, losing 1-0 to SSC Napoli at Stadio Diego Armando Maradona on Saturday evening.
I Bianconeri battled throughout a fiercely competitive match, and had the chances to break the deadlock in the first half, with Federico Bernardeschi notably blazing over the crossbar.
Alvaro Morata and Cristiano Ronaldo also failed to find a way past Alex Meret in the first half, and they were made to pay for their missed chances on the half-hour mark.
VAR was called into action after 30 minutes, when Giorgio Chiellini struck Amir Rrahmani across the face in the box, and after running to the screen at the side of the pitch, the referee awarded a penalty for Napoli.
Captain Lorenzo Insigne put the nightmares of the Supercoppa Italiana penalty miss behind him, crashing this spot-kick into Wojciech Szczęsny's top right corner, and handing under-fire coach Gennaro Gattuso a precious lead.
I Partenopei were then forced to defend for the entirety of the second half, as Juve put the pressure on to try and restore parity. Federico Chiesa came close to levelling the game, forcing a strong save from Meret between the Napoli sticks.
Morata thought he had equalised for the visitors, but his goal was ruled out due to Chiellini standing in an offside position. Ronaldo almost got the crucial equaliser on 74 minutes, but Meret was up to the task of sending his effort round the post for a corner.
And Napoli saw out the final minutes to secure a vital three points for the club and their coach Gattuso, whose job was reportedly on the line heading into this massive clash.
As for Juventus, they remain seven points behind leaders Milan, missing out on the opportunity to close the gap to only four points ahead of I Rossoneri's trip to Spezia on Saturday evening.