TAMPA, Fla. -- NFL Players Association executive director DeMaurice Smith said Tuesday the union is looking to investigate how Tampa Bay Buccaneers quarterback Josh Freeman's presence in Stage 1 of the league's substance-abuse program became public.

ESPN's Chris Mortensen first reported the news Monday night. Freeman later released a statement in which he said he has a prescription for Adderall to treat ADHD but that he inadvertently took Ritalin last year and it triggered a positive test. As a result of the positive test, Freeman submitted to frequent drug screenings, leading to his placement in Stage 1 of the league's drug program.

"We are sufficiently concerned about what we've heard to begin an investigation,'' Smith said after a previously scheduled annual meeting with Tampa Bay players.

On Tuesday, Buccaneers coach Greg Schiano was asked by reporters if he was the source of the information and said, "absolutely not."

"I know what I've done. I'm 100 percent comfortable with my behavior, 100 percent," he said.

Smith said his main concern was about the rights of all NFL players.

"We have a collective bargaining agreement that mandates and protects confidentiality and privacy,'' Smith said. "If we believe that any member of team management or anyone from the league has deliberately taken steps to thwart that privacy and to breach that confidentiality, this union will take every step and file every grievance and pursue any law to rectify that. We believe that it's important to maintain the confidentiality.