Napoli missed the opportunity to move top of Serie A after suffering a deserved 1-0 defeat at Udinese on Sunday.
The visitors had a chance to take first place after AC Milan earlier drew 2-2 at home to Sassuolo but Napoli struggled against an aggressive Udinese, who had two goals disallowed.
Napoli are second with 31 points, one point behind Milan and a point ahead of third-placed Inter Milan, who play at Genoa later on Sunday. Udinese are 10th with 21 points.
After a mostly uneventful first half, it was the hosts who tried to show they were the superior team after the break.
Keinan Davis thought he had given Udinese the lead minutes into the second half after running in on a rebound but the celebrations were short-lived as VAR showed he was offside.
With the pressure mounting, it seemed a matter of time before the breakthrough arrived. In the 69th minute, Udinese's Nicolo Zaniolo was slipped through on goal, surged to the edge of the box and drove a low shot into the net.
However, the referee ruled the goal out for a foul in the build-up, which drew furious protests from the home supporters.
Four minutes later Udinese's Jurgen Ekkelenkamp produced a moment of brilliance to put the home side ahead.
Collecting the ball at a tight angle near the edge of the area, he shrugged off a defender and curled a superb finish into the top corner.
Napoli got more involved in the closing stages after being outmatched for much of the second half.
Rasmus Hojlund came close when he arrived unmarked at the far post to meet a cross, but lost his footing and fell as his effort sailed over the bar.
Deep into stoppage time, Napoli had another chance as Lorenzo Lucca stretched to meet a cross inside the box but his effort struck the base of the post and went wide.