Denver Broncos wide receiver Wes Welker has been suspended for the first four games of the 2014 season for violating the NFL performance-enhancing substances policy.
The league never makes public what substances athletes test positive for but the 'Denver Post' reported it was the banned stimulant Adderall, a drug prescribed to treat Attention Deficit Hyperactivity Disorder (ADHD).
The news comes just five days before the Broncos, who lost last season's Super Bowl, begin their season with a home game against the Indianapolis Colts. In an email to the Post, Welker said he was "as shocked as everyone" and would fight to clear his name.
"I would NEVER knowingly take a substance to gain a competitive advantage in any way," he said.
"I have never been concerned with the league's performance enhancing or drug abuse policies because under no scenario would they ever apply to me.
"But I now know that (drug-policy procedures) are clearly flawed, and I will do everything in my power to ensure they are corrected, so other individuals and teams aren't negatively affected so rashly like this."
Welker, who has been to the Pro Bowl five times, is a key receiver for Denver quarterback Peyton Manning and made 778yards on 73 receptions last year.
The news cast something of a shadow over the opening week of the games which start in the early hours of tomorrow morning (Irish time) as SuperBowl champions Seattle Seahawks host the Aaron Rodgers-led Green Bay Packers.
Seahawks v Packers, live, Sky Sports 1, tomorrow, 1.00am