Veteran Fluminense midfielder Deco is seeking to clear his name after it emerged he tested positive to a banned substance.
The 35-year-old former Portugal international was found to have traces of the masking agent furosemide in test samples given after Fluminense's 2-0 victory over Boavista in Brazil's Campeonato Carioca March 30, reports Xinhua.
"His major concern is to protect his image," Deco's advisor Acaz Felleger said Tuesday.
"He has been taking a vitamin supplement for a long time and it seems like there was some kind of contamination. He is talking to his lawyers about taking possible legal action against the pharmacy."
Deco has been left out of Fluminense's squad for Thursday's Copa Libertadores round of 16 first leg against Emelec in the Ecuadorian city of Guayaquil.
Furosemide is a diuretic that acts by inhibiting the kidneys' ability to retain water and is banned due to its effectiveness in hiding other prohibited substances.
Deco has reportedly requested a secondary test, which is understood to be scheduled for Friday (April 3).
The former Porto, Barcelona and Chelsea star has helped Fluminense to two Brazilian Serie A titles since joining the club in 2010.