Porto and Sporting CP played out a 2-2 draw at the Estadio do Dragao on Friday, but wild scenes at the end saw four players shown red cards.
Sergio Conceicao’s Porto had come from 2-0 down to level the match and then went close to a 96th-minute winner when a corner almost fell to Pepe to score.
An overhead kick clearance saved the visitors, however, and Pepe went down holding his face.
Sporting’s players felt the former Real Madrid man was trying to buy a penalty, despite the final whistle having been blown, and soon numerous players and staff from both teams were squaring up on the pitch, with stewards and the officials attempting to restore calm.
Amid the melee, referee Joao Pinheiro sent off Pepe and Porto team-mate Agustin Marchesín, as well as Sporting duo Joao Palhinha and Bruno Tabata.
Sporting had already seen Sebastian Coates sent off early in the second half for two yellow cards.
After an early Paulinho header, a lovely team move ended with Nuno Santos making it 2-0 after 34 minutes as Sporting played from back to front, Pablo Sarabia eventually squaring for Santos to double Sporting’s lead.
Ruben Amorim’s side were eager for a win to close the gap in the Primeira Liga title race, but Fabio Vieira pulled a goal back just four minutes after Santos’s strike, before a Mehdi Taremi header with 12 minutes remaining levelled things.
Following the late drama, Porto stay six points clear of Sporting at the top of the table and moved 13 ahead of third-placed Benfica, who have played a game fewer than their two rivals.