Flamengo were knocked out on the pitch by Estudiantes.
But on Friday (23), they filed a complaint with Conmebol alleging that defender Marcos Rojo was ineligible to play at the Maracanã.
The Rubro-Negro believe they should be awarded the points from the match, which would secure them a place in the Libertadores final against Palmeiras.
Estudiantes reportedly have until next Monday (26) to submit their defense.
The information was reported by Argentine journalist Germán García Grova, of TyC Sports and Radio La Red.
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Rojo was an "emergency" signing by Estudiantes because two center-backs, González Pírez and Tomás Palacios, were suspended for the first leg.
Then a Racing player under contract until December, he left the club headed by Diego Milito in acrimonious circumstances.
Estudiantes agreed to pay $500,000 to secure the 36-year-old veteran's immediate release.
They will also pay a $250,000 bonus for reaching the final. And they could pay another $450,000 if they win the title.
Conmebol ultimately barred him from playing in the first match against the Rio de Janeiro club.
Unhappy with that decision, Estudiantes then turned to the Court of Arbitration for Sport (CAS), which cleared the player to take part one day before the second leg.
Rojo, a product of the La Plata club's academy, was one of three center-backs fielded by Cacique Medinda and was replaced by Tomás Palacios in the 77th minute.
This article was translated into English by Artificial Intelligence. You can read the original version in 🇧🇷 here.