Substitute Cicero scored the only goal as Brazilian side Gremio defeated Argentina's Lanus 1-0 in the first leg of the Copa Libertadores final on Wednesday.
A stormy encounter in Porto Alegre was settled seven minutes from time when Cicero pounced on a headed knockdown by Jael.
Cicero, who had replaced Jaja midway through the second half, latched onto the loose ball and steered his shot past Lanus goalkeeper Esteban Andrada.
It was the decisive act of an ill-tempered between the Brazilian and Argentinian clubs in the showpiece game of South American club football.
Seven players were cautioned throughout the game, with Chilean referee Julio Bascunan being surrounded by players from both sides at the final whistle.
Gremio had dominated for long periods of the game but struggled to create many chances before Cicero's winner.
Lanus almost took the lead in the first half but Diego Braghieri's powerful downward header was brilliantly saved by Gremio goalkeeper Marcelo Grohe.
The build-up to the first leg had been dominated by controversy, with Gremio accused of hiring a scout to spy on opponents during training sessions.
ESPN Brasil reported that the individual recruited had used a variety of techniques including drones and cameras hidden in trees, buildings and walls to glean information on rival teams.
The second leg of the final takes place on November 29.