I don't expect lot of goals on this match. The reason is very simple, both teams have many absent players. And the best among them. Flamengo key player Ronaldinho is with Brazilian national team. His absence is big handicap for the hosts. But that's not all as three more players are suspended - Airton, Willians and Gustavo. Coach Vanderlei Luxemburgo will be on big troubles, I don't think he has an adequate replacements for them. On other hand Fluminense is also missing the key player as Fred, just like Ronaldinho, is with the national team. One more player, Gum will miss the game due to injury. In situation like this I don't expect something special from the players from both teams. So, I think Under 2.5 goals is a good option for this match. Even the last three mutual matches ended that way:

Campeonato Brasileiro 2011������
10.07.2011. Fluminense - Flamengo 0:1

Campeonato Carioca 2011
24.04.2011. Fluminense - Flamengo 1:1 (1:2 AET)
13.03.2011. Flamengo - Fluminense 0:0

I expect something similar now.