Lazio's fading Serie A title challenge suffered a potentially fatal blow when they lost 2-1 at relegation-threatened Lecce and their frustration boiled over as defender Patric bit an opponent and was sent off in the closing moments on Tuesday.
Headed goals from Khouma Babacar and Fabio Lucioni gave Lecce the win which left second-placed Lazio seven points adrift of Juventus, who were playing at AC Milan later on Tuesday. In between, Mancosu missed a penalty for the home side.
A chaotic game ended with 10 minutes of added time which included a red card for Patric after replays showed that the Spaniard bit Guilio Donati's arm.
Lazio, suffering from having a small squad and ravaged by injuries, stayed seven points behind leaders Juventus after losing for the third time in five games since the season restart. Lecce are a point above the bottom three, having played a game more than 18th-placed Genoa who host Napoli on Wednesday.
There was drama from the outset as Lecce's Marco Mancosu burst upfield and rifled a left-foot shot into the top corner, but it was chalked off after a long VAR review because the ball brushed Mancosu's hand as he controlled it in the centre circle.
That should have suited Lazio's counter-attacking style but they left Babacar unmarked to head in Filippo Falco's cross on the half hour and then conceded a penalty in first-half stoppage time.
Marco Calderoni's cross hit Patric on the arm as he slid in to block the ball and the referee pointed to the spot but, as Mancosu was about to take the kick, he decided to review the incident. The decision was confirmed after a two-minute delay but Mancosu appeared distracted and fired his effort over the bar.
Lazio's relief was short-lived as Lucioni headed Lecce in front from a corner two minutes after halftime.