Lazio confirmed their title credentials on Saturday evening with a dogged 1-0 victory over Napoli, but the Eagles were gift-wrapped the three points through a howler from goalkeeper David Ospina.
The two sides played out a tense first half, in which the hosts had the better of play, with chances falling to the feet of both Felipe Caicedo and Ciro Immobile, though both Lazio forwards fluffed their lines.
Napoli looked more organised under new coach Gennaro Gattuso but they lacked imagination and creativity in front of goal, while occasionally gifting possession to their opponents in dangerous areas.
The second half was as equally hard-fought as the first, and despite struggling to carve out many chances, Napoli almost pinched a dramatic lead through Piotr Zielinski. The Polish midfielder danced through a couple of tackles and aimed a bending effort towards goal, but his curler hit the post and rebounded to the feet of a Lazio defender.
The away side grew into the game and Gattuso's men looked the more likely to break the deadlock as the minutes ticked by. And in a game that could only be decided by a moment of brilliance or comedy, the latter struck in the hosts' favour.
Napoli shot-stopper Ospina dallied in possession in his own penalty area, and rather than booting the ball into the stands, the Colombian tried to play his way out of trouble.
Lazio striker Immobile was not fooled by Ospina's footwork, however, and having dispossessed the second-choice goalkeeper, the striker lashed the ball into an empty net to send the home fans into pandemonium.
It was a moment to forget for Ospina, but unfortunately for Gattuso and his shot-stopper, it was the decisive action in a tense match.