Napoli have the Milan giants breathing down their necks in the Serie A title race after throwing away a two-goal lead late at Sassuolo to draw 2-2 on Wednesday.
Luciano Spalletti's side looked set to maintain their three-point lead at the top of the league following second-half strikes from Dries Mertens and Fabian Ruiz.
But a superb finish from Gianluca Scamacca with 19 minutes remaining put the hosts back in the game and Gian Marco Ferrari snatched a draw in the final minute with a bullet header.
Sassuolo thought they had won it in a franctic finale in which Napoli coach Luciano Spalletti was sent off when Gregiore Defrel slotted home the third. But with the home players and fans celebrating wildly, the referee was called to check a Domenico Berardi foul on Amir Rrahmani and the goal was ruled out.
To make matters worse for Napoli, who host high-flying Atalanta on Saturday, they lost both scorers and defensive lynchpin Kalidou Koulibaly to injury.