Former Barcelona, Chelsea and Porto star Deco has failed a doping test while playing for Fluminense.
The former Portugal international tested positive for banned substance Furosemide following Flu's clash with Boavista on March 30.
The 35-year-old has not travelled with the squad for their Copa Libertadores clash with Emelec in Ecuador this Thursday.
Deco is believed to have ingested the substance through vitamin supplements, which he purchased at a pharmacy.
Reports in Brazil claim he has appointed solicitors to take action against the company that produce the product he bought.
The news comes just two weeks after another doping case hit Brazilian football, when Vasco da Gama midfielder Carlos Alberto tested positive for two banned substances following a 3-2 win over Deco's Fluminense side in early March.