Jarvis Jenkins has been handed a four-game suspension for violating the NFL's policy on performance-enhancing substances.
The Washington Redskins defensive end has claimed that the substance entered his body through an over-the-counter supplement.
He told The AP: "The NFL has strict rules. They tell us we're responsible for what's in our body. Obviously I'm being led as an example."
The 25-year-old played in all 16 regular season games for the Redskins last season, making 25 tackles in the process.