Charles Johnson has been suspended four games for violating the league's policy on performance-enhancing substances.

Johnson has started all 11 games this season for the Carolina Panthers. He has 16 tackles and no sacks.

"I accept full responsibility," Johnson said in a statement released by the team. "I have been recovering from back surgery, dealing with the daily grind of football and mistakenly thought this could help. It was an error in judgment on my part.

"We have a special group here I wanted to be a part of and felt an obligation to do my part by getting back as soon as possible. I have always prided myself on being a person who does things the right way, through hard work, dedication and sacrifice. I want to apologize to my team, Mr. [Jerry] Richardson and Panthers fans for this mistake. Regretfully, I have disappointed people, but I promise to come back ready to redeem myself when this suspension is over."