The NFL has announced that it will suspend uncooperative players in its PED investigation.

The National Football League, which cleared Peyton Manning of any wrongdoing in the investigations into PED use, has warned the four other players accused that they must cooperate.

The NFL performance enhancing drug probe is looking for the players, which include Super Bowl champions, James Harrison and Clay Matthews, to conduct interviews with investigators by August 25.

Julius Peppers and Mike Neal join the other two players in risking being suspended as early as August 26 if they do not comply with the demands of the probe.

NFL senior vice president of labor policy and league affairs, Adolpho Birch, made this fact abundantly clear to the NFL Players Association.

All four players submitted official affidavits to the NFL in July claiming their innocence.

“Since the initiation of our investigation in January the league has made at least seven attempts to arrange interviews of Messrs. Harrison, Matthews, Neal and Peppers,” read the letter. “On each occasion, the NFLPA has communicated the players’ refusal to participate….Rather than eliminate the need for interviews, the players’ plainly deficient statements simply underscore the importance of obtaining their full cooperation.”

Reports of the performance enhancing drug use in the NFL began in a documentary titled, The Dark Side.

The documentary, published by Al Jazeera America, alleged that the four players and Peyton Manning had received and used the drugs. All denied the charges.

Charlie Sly, the anti-aging clinician who implicated the players in the documentary, later recanted his story.