A person familiar with the case says Broncos All-Pro linebacker Von Miller was caught trying to manipulate the NFL's drug-testing system.
The person spoke on condition of anonymity Sunday because the league has not announced the details of Miller's violation. The manipulation attempt was first reported by ESPN.
Miller is suspended for the first six games of the season under the NFL's substance-abuse policy.
When his ban was announced last month, Miller said in a statement, "although my suspension doesn't result from a positive test, there is no excuse for my violations of the rules."
NFL spokesman Greg Aiello declined to comment on Miller's situation.
Miller has also had several other off-field problems. He was cited earlier this month for speeding and driving with a suspended license.