The 35-year-old former Brazil international is in line to make his first appearance for his club this weekend after impressing in training this week.
Former Brazil international Ronaldinho could make his Fluminense debut against old club Gremio this weekend.
The 35-year-old former World Player of the Year trained with his new teammates for the third time on Wednesday and coach Enderson Moreira has confirmed the World Cup winner is in contention for Saturday's Brasileirao showdown at the Maracana on Saturday.
Ronaldinho sealed his return to Brazil earlier this month after a year with Mexican club Queretaro but was given two weeks' holiday before reporting for training.