Arizona Cardinals cornerback Patrick Peterson is being suspended the first six games of the 2019 season for violating the NFL's performance-enhancing drug policy, league sources told ESPN on Thursday.

Details of what Peterson did, and when he did it, remain confidential, as per the NFL's PED policy. But the eight-time Pro Bowl selection dropped his appeal, and the suspension is expected to be officially handed down at some point in the next week, a source told ESPN.

Peterson will miss Arizona's regular-season opener vs. the Lions, then games at Baltimore, at home against the Panthers and Seahawks, at Cincinnati and at home against the Falcons.

He will be eligible to return Oct. 20 at the New York Giants.

Earlier this month, on The Adam Schefter Podcast, Bengals wide receiver A.J. Green called Peterson the best cornerback in the league.

Peterson has started all 128 games since being drafted by the Cardinals in 2011, and his 23 interceptions are tied for third-most in the NFL.

The three-time All-Pro did not report to the Cardinals' voluntarily minicamp last month because he was upset with the team. There has been trade speculation regarding Peterson, but now he is not scheduled to be reinstated until shortly before the NFL's trade deadline.

At his pre-draft news conference last month, Cardinals coach Kliff Kingsbury said he was not concerned about Peterson's absence from this spring's camp.

"It's voluntary," Kingsbury said last month. "I communicated with Patrick. We know where he's at and we know what's going on. Kind of a conversation to keep between ourselves. If he hadn't communicated and we didn't know what was going on, I think that would be a different matter. It is a voluntary camp. We know that Patrick wants to be here and wants to be a part of this team."

Arizona has been aware of Peterson's pending suspension, and the Cardinals used the 33rd overall pick in last month's draft on Washington cornerback Byron Murphy.

Peterson has two years left on his contract and is set to make a base salary of $11 million this season and $12.05 million in 2020. This six-game suspension is set to cost Peterson $3,882,352 in lost wages.