Today's unanimous vote by the appeals tribunal of the Superior Court of Sporting Justice confirms Fluminense will play in Brazil's Serie A next season despite finishing in the bottom four.
It saves Flu from the ignominy of becoming the first team to be relegated a year after winning the league title.
Portuguesa made their mistake in the last game of the season and were docked four points for playing midfielder Heverton before he had sat out both games of a two-match suspension.
It is not the first time Fluminense, traditionally the club of Rio de Janeiro's white elite, have been saved from the second division by controversial off-the-field decisions.
In 1999, the team won Serie C and were scheduled to play in Serie B the following year. However, an unanticipated reform of the league format saw them lifted straight into the first division.