Leaders Fluminense lost 2-1 away to 10-man Atletico Goianiense but are still three points ahead of Corinthians, who suffered their first home defeat of the season, 1-0 to Gremio.
In a match they had been expected to win against a team in the relegation zone, Flu went ahead after 23 minutes when Washington finished a move involving playmakers Deco and Argentine Dario Conca.
Things looked to become easier for Flu when the home side's defender Gilson was sent off for a foul on Carlinhos, his second booking, but substitute Juninho scrambled in a winner in stoppage time.
"We should have won today's game. We knew Corinthians were losing and the chance was very big to open a bigger distance from them," disappointed Flu coach Muricy Ramalho told reporters.
"Now we must prepare the team for Wednesday. It's a match against a direct rival for the title and we must win it whichever way possible."
