Atlanta Hawks forward John Collins has been suspended for 25 games for breaching the NBA's anti-doping rules.
The 22-year-old tested positive for Peptide-2, a drug that increases the release of a growth hormone.
Collins told ESPN he plans to appeal against the suspension, which is set to begin when the Hawks face the San Antonio Spurs on Tuesday.
"I am incredibly frustrated and disappointed in myself for putting all of us in this position," said Collins.
"I have always been incredibly careful about what I put in my body, but I took a supplement which, unbeknownst to me, had been contaminated with an illegal component."
Collins is the third NBA player to be given a 25-game ban for breaching drug regulations this season.
Phoenix Suns centre Deandre Ayton was suspended last month after testing positive for a diuretic.
In August, Brooklyn Nets forward Wilson Chandler tested positive for Ipamorelin, another drug that increases the release of growth hormone.