Neymar was sent off before half-time as Santos drew 1-1 with Bahia in the 32nd round of the Brazilian league.
The match was played at Santos’ home ground, where the dismissal followed an incident involving Santos midfielder Rodrigo Nestor and a Bahia player.
Nestor pushed Neymar near the goal-line, after which Neymar stood up and threw the ball towards the Bahia player. The referee initially showed him a yellow card as players from both sides became involved in a verbal confrontation.
The official then reviewed the incident using video technology. The footage showed Neymar covering his mouth while speaking with Nestor, prompting the referee to change the decision and send him off.
The rule allowing a player to be dismissed for covering his mouth while speaking has become known as the “Vinicius law”. It was introduced after Vinicius claimed he had been subjected to racist insults by Benfica player Prestianni while covering his mouth during their exchange.
The rule was applied at the World Cup, although responsibility for deciding whether to use it now rests with each football association.
Santos are sixth in the Brazilian league with 46 points, five points behind fifth place, which qualifies for the Copa Libertadores.
Vinicius will be absent following the dismissal from the Brazilian classico between Santos and Palmeiras.
