Denver Broncos wide receiver Wes Welker has been banned for four games by the NFL after testing positive for a banned amphetamine.
Welker helped the Broncos reach the Super Bowl last season, where they were eventually defeated by the Seattle Seahawks.
In an email sent to the Denver Post, Welker protested his innocence stating he "never knowingly" took anything and said that the procedures are "clearly flawed".
"I'm as shocked as everyone at todays news," the email read.
"I want to make one thing abundantly clear: I would NEVER knowingly take a substance to gain a competitive advantage in any way. ... I have never been concerned with the leagues 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 caught 73 passes and 10 touchdowns for the Broncos last season, as part of one of the best offences in league history.
The Broncos have also seen kicker Matt Prater banned this off-season for repeated alcohol violations.
Welker has already had an appeal rejected but will appeal again. However he may not be available until Denver's Week 6 game at the New York Jets.
"Tonight's news regarding Wes is very disappointing for our team, but we understand the league's authority in this area," Broncos head coach John Fox added.
"While it's unfortunate to not have him to start the year, I have full confidence in our wide receivers and expect that group to continue playing at a high level. I have no doubt that Wes will remain focused on his preparations for the season and stay in excellent shape during his time away from the team."