The Brazilian champions were glad of the boost at Rio's Olympic Stadium having struggled to beat equally modest Bangu 1-0 in their opening match of the season on Thursday.
Captain Fred, who like Deco spent the better part of last year nursing injuries, had an encouraging performance scoring two goals and laying on another.
Midfielder Marquinhos scored twice standing in for Argentine Dario Conca, Brazil's 2010 Player of the Year who had knee surgery last month, and substitute Rodriguinho also hit two.
But former Porto, Barcelona, Chelsea and Portugal midfielder Deco, yet to justify being the team's highest paid player, did not appear to have overcome his woes as he came off with a left thigh injury.
There was scarce interest from fans in Flu's match, as is generally the case when the big clubs face small teams in the state championships that open the Brazilian season in mid-summer. Only a major derby can be expected to draw big crowds before the national championship starts in May.
No doubt, there will be a big crowd when Fluminense clash with Flamengo with the added spice of their rivals having just signed Ronaldinho, who is expected to be fit enough for his debut next month.
In the Paulista (Sao Paulo) championship, midfielder Elano scored twice for title holders Santos in their 4-2 win over Gremio Prudente to notch a third consecutive win.
They are without young talents Neymar, who is playing for Brazil in the South American under-20 championship in Peru, and Paulo Henrique Ganso, still recovering from knee surgery.
