Down 1-0 to Udinese in the final minute of added time, Lazio brought goalkeeper Federico Marchetti forward on a last-chance corner kick. Though Marchetti swung his head at the ball, nothing came of the corner and he had to jog back to his own goal.
Moments later, an Udinese clearance was followed by what sounded like the final whistle came from the crowd. Many of the player stopped, thinking the match was over, but Udinese's Roberto Pereyra didn't. Instead, Pereyra took a shot from outside of the box after Marchetti had abandoned his net and scored to put Udinese up 2-0. As Udinese celebrated, Lazio protested and shoved a couple of the officials.
It took about five minutes for enough calm to be restored so the match could resume and the ref could blow the actual final whistle. After the match, Lazio refused to speak to the press, but Udinese midfielder Giampiero Pinzi gave his account (via Football Italia):
"I heard a whistle from the crowd. The Lazio players suddenly stopped and thought it was the referee," Udinese midfielder Pinzi told Mediaset Premium.
"Pereyra continued and perhaps had realised it wasn't the official. In all honesty, I'm not sure what the rule book states in these cases, but the game would've finished with that move anyway.
"It's a shame there was this mark on the night after a great performance."
In the end, Pinzi is probably right that the incident didn't change the outcome, but from now on Lazio will probably play a good five minutes past any whistle they hear from the referee or otherwise.